Photodegradation Of Tebuconazole In A Fluidized Bed Reactor Mediated By Phenalenone Supported On Sand

This study reports on the photodegradation of tebuconazole (TEB) within a fluidized bed pilot unit mediated by phenalenone (PN) grafted on sand (PN-sand). The photodegradation experiments were conducted in both a cylindrical laboratory-scale reactor and a fluidized bed pilot unit equipped with a lit LED strip, for reactional volumes of 0.4 L and 38.7 L, respectively. The lab reactor study showed that TEB removal was slightly affected by the LED emission type, i.e. purple LEDs (380 nm-440 nm) and blue LEDs (435 nm-465 nm). The PN-sand loading also affected TEB removal, with a maximum rate of 79% at a loading of 30 g.L-1, corresponding to a PN/TEB molar ratio of 1800. TEB photodegradation could be described by a first-order kinetic constant of (1.1 +/- 0.2) x 10(-3) min(-1) with a first step where photodegradation was coupled to a rapid sorption.Similar kinetic constants were observed in both reactors. A recirculation flow of 440 L.h(-1) made it possible to assimilate the fluidized bed reactor into a perfectly stirred reactor. Experiments were conducted with this recycling flow and an inlet flow of 1.1 L.h(-1) and 4.2 L.h(-1), respectively. The use of the first-order kinetic constant of 1.0 x 10(-3) min(-1) in a CSTR reactor served to propose a reactional model for the TEB solution photodegradation. A drift towards the model was detected after a contact time of 33 h and independently of the residence time. A degradation of phenalenone or a decrease in active phenalenone took place by photobleaching or ungrafting from the support.