Photocatalysis of naphthalene by Fe₃O₄/Oxone/UV: Simultaneous radical and non-radical pathways

Naphthalene (Nap) degradation by photocatalysis of Fe3O4/Oxone/UV was studied. The system eliminated Nap in 30 min and the kinetics is described by a novel mixed order model with adsorption and decay dominant rate constants, representing non-radical and radical pathways respectively. The reaction is dominated by catalysis in acidic pHs as Oxone anions are adsorbed onto the protonated Fe3O4 surface for activation; In alkaline solution, the adsorption of Nap to the deprotonated Fe3O4 surface is the main removal pathway. The catalyst was reused for 5 cycles and the performance was enhanced after reuse. XPS study confirmed that the surface Fe content of Fe3O4 remained stable after reusing due to the effective UV-assisted FeII - FeIII catalytic cycle. An additional C=O bond on Fe3O4 surface was detected after reuse, which is proposed to be an OH bond on catalyst as an extra adsorption site and for radical generation.