In-situ UV absorption spectroscopy of ozone in gas phase and in water
J.-S. Oh1,2, H. Yajima3, K. Hashida1, K. Ogawa1, I. Serizawa3, H. Furuta1,2, A. Hatta1,21

Dept. of Electronic and Photonic Systems Engineering, Kochi University of Technology, Kami, Kochi 782-8502, Japan,
E-mail:jun-seok.oh@kochi-tech.ac.jp
2
Center for Nanotechnology, Research Institute of Kochi University of Technology, Kami, Kochi 782-8502, Japan3
ORC Manufacturing Co., Ltd., Chino, Nagano 391-0011 JapanUsing an in-situ UV absorption spectroscopy, we measured UV absorption spectra of O3 in the both gas
and liquid phases. The analysis of UV absorption spectra indicated the generation of H2O2 and O2 withO3, and the concentration O2 in the early stage played an important role in generation of O3.

1. Introduction
Ozone (O3) is a well-known molecule as astrong oxidant and it can be generated by O2 flow (and /or air) through electrical discharge. [1] In recent, O3 isgetting important in many applications including life
science as well as the traditional water treatment, aircleaning, semiconductor and industry. [2]For the measurement of the absolute concentration ofO3 is well established based on the light absorption
technique for measuring an absorbance at a fixedwavelength. It is common that the measurements of theboth gaseous O3 and O3 in water associate with a UV at
254 nm from a mercury lamp. Also, a combination of achemical probe and a LED light for detecting thechange of color at a fixed wavelength is open used for
dissolved O3 in water. However, these methods unable
to support sufficient information to understand thecomposition of species in gas or liquid.
Here, we used a traditional method of UV absorption
spectroscopy to detect O3 and other species in gas andwater. Also, we will discuss the evolution of O3
generating process using in-situ measurement.

2. In-situ UV absorption spectroscopy
A conventional UV-Vis spectrophotometer (U3900, Hitachi) was used for detecting O3 in the both gasFig. 2: UV absorption spectra of gaseous O3 anddissolved O3 in water with a reported spectrum.
and liquid phases (in Fig.1). O3 generated through an O2
creeping discharge and delivered into a quartz tube1 forgaseous O3 or a quartz cuvette for O3 in water. Fig. 2
shows the absorption spectra of stable O3 measured inthe both phases. It noted that the spectrum of O3 inwater (or ozonated water) has the absorption peak atslightly longer wavelength of 260 nm and shows anabsorption shoulder at short wavelength range below
220 nm as compare to the spectrum of gaseous O3. [3]Form the analysis of in-situ measurements of O2 plasma
bubbling in water for 12 min, we found that there aremuch high concentration of H2O2 (42 mg/L) and O2 (3mg/L) with O3 (9 mg/L). Also, the concentration ofdissolved O2 in water played an important role ingeneration of O3 at an early stage.

References[1] I. Somiya, Ozone Handbook, Japan Ozone Association,Tokyo (2004) in Japanese.
[2] C. Gottschalk, J. A. Libra, A. Saupe, Ozonation of
Water and Waste Water, Wiley-VCH, Weinheim (2000).
[3] R. Suzuki, Readout, 25 (2002) 29–31 in Japanese.
1Fig. 1: Schematic of the experimental set-ups to monitor
the gas phase O3 (lhs) and O3 in water (rhs).

Quartz tubes for detecting gaseous reactive molecules
were provided by Mr. S. Shioya and Mr. T. Hayakawa
of ORC Manufacturing Co. Ltd.