Indoor air treatment of refrigerated food chambers with synergetic association between cold plasma and photocatalysis: Process performance and photocatalytic poisoning

The purpose of this study is to evaluate the efficiency of non-thermal plasma (NTP) and heterogeneous photocatalytic processes for indoor air treatment of refrigerated food chambers. Propionic acid and benzene were chosen as target pollutants to simulate odors inside a fridge. Firstly, the microstructure of the used catalyst was investigated by transmission electron microscopy (TEM). The influence of operating parameters such as pollutant concentration, type of system (mono-compound or bi-compound system), duration of photocatalytic degradation and relative humidity in the indoor air were investigated. Our findings show a synergetic effect between NTP and photocatalysis for malodors removal. Additionally, the mineralization of pollutant is directly controlled by the amount of ozone produced by the plasma discharge then it decomposes on the TiO2-based catalytic surface. Our results highlight also the key role of the generated reactive oxygen species (hydroxyl radials and atomic oxygen) in (i) propionic acid and benzene removal, (ii) selectivity of CO2 and CO, (iii) byproducts formation such as ozone formation. Moreover, the recovery of the initial photocatalytic activity was explored in details. A significant poisoning occurred when photocatalysis was carried out alone for the degradation of propionic acid and benzene. Results confirm that NTP plasma enhanced the photocatalytic activity. We also showed the effect of NTP plasma on the regeneration of the photocatalytic surface.