New UV-flux measurement method using ozone photolysis rate

This study focuses on the evaluation method of UV energy flux and other necessary design parameters in the Ozone/UV process. The UV energy sources used for the Ozone/UV process are the low-pressure Hg arc at 254 nm and the high-powered medium pressure Hg arc. This paper suggests a new method of measuring photonic flux, called ozone-actinometry, by measuring continuous ozone decay rate in the photo-reactor. For precise measurement of the absorbed photon, an experimental set-up equipped with a continuous sample taking and detection of aqueous residual ozone by spectrophotometric method (using molar extinction coefficient of ozone: ε= 3300 M^-1 cm^-1 at 254 nm) was employed for the kinetic tool. The result of this newly developed ozone-actinometry set-up enabled the authors to measure UV intensity (I_o) and quantum yield of ozone (Φ_O3) which are key parameters needed for the photo-reactor design of Ozone/UV process. The quantum yield of the direct photolysis rate of ozone at 254 nm is measured to be 0.78, the value of which is higher than the previously reported value of 0.62. The performance of two different UV sources was also evaluated.