UV-LEDs floating-bed photoreactor for the removal of caffeine and paracetamol using ZnO supported on polystyrene pellets

In this paper a UV-LEDs floating photocatalytic reactor was developed in order to remove caffeine and paracetamol from water using ZnO immobilized on low density macroscopic polystyrene pellets as floating photocatalyst. Different amounts of ZnO were immobilized on polystyrene pellets surface by solvent casting method and characterized from chemical-physical point of view using N2 adsorption at -196 °C, SEM analysis and XRD technique. Photocatalytic activity results evidenced that, during the irradiation time, the photocatalytic performances with the floating-bed reactor were strongly enhanced with respect to the fixed-bed reactor. The influence of process parameters, such as ZnO amount immobilized on polystyrene pellets, air flow rate and UV light intensity, has been investigated. The results showed that the complete caffeine degradation with a mineralization degree of about 86% was achieved after 240 min of UV irradiation at ZnO loading on polystyrene pellets of 1.1 wt%, air flow rate of 144 Ncc·min−1 and UV light intensity of 13 W·m−2. Furthermore, the optimized photocatalyst can be reused for several cycles without any substantial decrease of photocatalytic performances. Finally, the floating photocatalyst was able to remove simultaneously paracetamol and caffeine from drinking water with a very good efficiency.