Ethylene photocatalytic degradation using TiO2 immobilized in a NETmix mili-photoreactor

Ethylene oxidation by TiO2 photocatalysis was studied in a mili-photoreactor (NETmix), as a potential clean postharvest technology to scavenge ethylene from fruit. The NETmix photoreactor comprises a stainless steel slab imprinted with a network of cylindrical chambers interconnected by prismatic channels, sealed by a UVA transparent borosilicate slab (BS), and a UVA LED plate paced above the reactor window. A thin film of the photocatalyst was immobilized in the NETmix network or on the side of the borosilicate slab in contact with the ethylene gas stream. Ethylene oxidation in single-pass mode (continuous operation) was evaluated as a function of TiO2 crystallinity, TiO2 loading, radiant power, illumination mechanism, feed stream composition (ethylene and water concentration), and flow rate. The catalyst loading and deposition surface, and relative humidity (RH) of the feed stream strongly affected the ethylene conversion, mineralization, and reaction rate. Even under severe conditions (RH = 25% and Qfeed = 571 cm3 min−1 for the back side illumination), the NETmix removed at least 0.11 μmolethylene min−1. The high efficiency of the photocatalytic NETmix reactor allows the removal of ethylene from the storage system at the beginning of fruit ripening, the period of the highest gas production, enabling it to be used as a promising technology in controlling fruit ripening.