Reaction and diffusion of chlorine dioxide gas under dark and light conditions at different temperatures

Chlorine dioxide (ClO₂) gas is a powerful oxidizing agent in many industrial applications for food processing, drinking water and cleaning treatments. It is considered for use in an increasing number of fresh food applications over a wide range of temperature and pH conditions due to its sanitizing capability. During the disinfectant treatment in a closed chamber or packaging system, ClO₂ gas is typically exposed to environmental factors such as light, temperature, and humidity which influence its disinfectant efficiency. Determining ClO₂ gas reaction rates and mass transfer properties are extremely important for the design of proper sanitization treatments. The aim of this work was to determine the diffusion coefficient for ClO₂ gas in air and reaction rates under dark, UV-A and fluorescent lamp exposure. The effect of temperature on the diffusion of ClO₂ was also assessed. A system was designed to measure these properties. The diffusion coefficient was found to be 0.129, 0.145, 0.173 cm² s^-1 at 5, 23, and 40 °C, respectively. Degradation of ClO₂ gas under dark, UV-A and fluorescent lamp exposure was found to follow a first-order reaction. Degradation using a 40 W UV-A lamp was approximately four orders of magnitude larger than with a 34 W fluorescent lamp. A methodology is proposed for quantifying the amount of ClO₂ gas needed in a package and/or treatment chamber.