Mechanistic evaluation and reaction pathway of UV photo-assisted Fenton-like degradation of progesterone in water and wastewater

The mechanisms and reaction pathway of UV photo-assisted Fenton-like degradation of progesterone in water and wastewater were investigated. The reaction followed the pseudo-first-order kinetics for both the dark Fenton-like and UV photo-Fenton-like processes. The reaction kinetics of the UV photo-assisted process improved with the presence of humic acid (HA) in wastewater, due to the formation of Fe(III)-HA complexes which enhanced Fe(II) production by a ligand-to-metal charge transfer. The UV photo-assisted process reduced the amount of ferric required to completely degrade progesterone by 60 % and lowered the activation energy to 42 kJ/mol compared to 104 kJ/mol for the dark Fenton-like process. Complete degradation of progesterone was achieved through a multi-step process involving several intermediate compounds.