Geração de contaminantes em ozonizadores de pequeno porte e degradação catalítica do ozônio em ambientes internos

Abstract

Ozone is highly oxidizing and pollutes at tropospheric level, causing damage to human health and the environment. Ozone can be used in a wide range of applications, from medicinal and veterinary applications (ozone therapy), treatment of water, effluents and soil, to decontamination of surfaces and indoor environments. The most common ozone production process is Dielectric Barrier Discharge (DBD). In this process, purified ambient air can be used as a feed gas, but it can generate undesirable nitrogenous contaminants. In this context, this study aims to assess the generation of contaminants in small-scale ozonators, as well as to evaluate the degradation of O3 by different catalysts. Contaminant generation was assessed using two different analytical techniques (iodometry and spectrophotometry) in gas and aqueous phases. The results showed that the iodometric method for determining O3 is significantly influenced by nitrogen contaminants. In addition, it was found that an increase in relative humidity and temperature caused a decrease in O3 production. Different catalysts were evaluated for ozone degradation: graphene oxide (OG), reduced graphene oxide (OGr), zeolite 4A modified with Mn (Z4A-Mn), granular activated carbon (CAG) and macerated activated carbon (CAM) and commercial catalyst (containing Mn). Ozone concentrations ranging from 0.077 ppm to 2.0 ppm and a flow rate of 3 L min-1 were tested for up to 60 min. OGr (1st batch) produced the highest reaction rate at 39 x 10- 6 mol gcat-1 min-1, at a concentration of 2.0 ppm of O3. The factors that probably contributed to the difference in O3 degradation efficiency were the time of exposure to the environment, storage, chemical composition and morphology of each catalyst