UV-irradiated fly ash-catalyzed Fenton-type process for the removal of paracetamol in wastewater: nickel, copper, and manganese as active sites

This study investigates the application of a photocatalytic process involving fly ash (FA) as a Fenton-like catalyst (without iron) for the removal of paracetamol (Para) in water. The active sites in Fenton-type reactions were found to be the trace metals in FA such as nickel, copper, and manganese. Furthermore, the removal efficiencies of the synergic process (UV-FA + H2O2) were compared with UV alone, FA, FA + UV, FA + H2O2, and H2O2 alone. Moreover, the effect of different pH, catalyst dose, a hydroxyl radical scavenger, and the effect of hydrogen peroxide dose was investigated. Para removal efficiency by different processes were found out to be Fly ash + UV + H2O2 > Fly ash + H2O2 > Fly ash > Fly ash + UV > UV. The adsorption of para on fly ash was found to have no significant effect on removal efficiencies. The optimum conditions were found out to be pH = 3, 8 mM concentration of H2O2, 0.2 g dose of fly ash for the synergic process. Although the synergic process was the best at pH 3, however, even near wastewater pH it was found to be effective. It is therefore concluded that fly ash + UV + H2O2 based synergic process is effective for the removal of pharmaceuticals even near wastewater pH.