Photocatalytic degradation of paraoxon-ethyl in aqueous solution using titania nanoparticulate film

Photocatalytic degradation of paraoxon-ethyl (o,o-diethyl o-(4-nitrophenyl) phosphate), a well known surrogate of chemical warfare agents, in aqueous solution was studied by using titania nanoparticulate film. Reaction followed pseudo first order behaviour. Photolytic degradation reaction of paraoxon-ethyl demonstrated relatively low rate with a value of rate constant of 2.5 × 10− 3 min− 1. Whereas, degradation reaction in the presence of titania nanoparticulate film and UV light displayed enhanced rate with a value of rate constant of 6.9 × 10− 3 min− 1 due to photocatalysis. Gas chromatography–mass spectrometry analysis showed the formation of p-nitrophenol, o,o-diethyl phosphonic acid, o-ethyl, diphosphonic acid, phosphoric acid, dimerized product of o,o-diethyl phosphonic acid, acetaldehyde, and carbon dioxide due to photocatalytic degradation of paraoxon-ethyl. It indicates that, photocatalytic degradation reaction begins with destruction of P–O–C bonds. Subsequently, P, C atoms were found to be oxidized gradually, and contributed to its photocatalytic degradation.

► Synthesis of titania nanoparticles by sol–gel method.
► Fabrication of titania nanoparticulate film by dip coating.
► Paraoxon ethyl degradation reactions followed pseudo first order behaviour.
► Paraoxon-ethyl degraded to non toxic compounds like CO2, acetaldehyde, and nitrophenol.