Photodegradation of Pb-3,4-dihydroxybenzoic acid complex under UV light illumination

The degradation of 3,4-dihydroxybenzoic acid (3,4-DHBA) in the presence and absence of Pb(2+) under UV illumination was studied. Addition of Pb(2+) caused the formation of precipitate during photoreaction when the solution pH was higher than 6. The presence of Pb(2+) remarkably inhibited the degradation of 3,4-DHBA and its photodegradation intermediates, while complexation of 3,4-DHBA and its photodegradation intermediates with Pb(2+) decreased the free Pb(2+) in aqueous solutions. Molecular oxygen played an important role in photodegradation of 3,4-DHBA in the presence of Pb(2+). UV-Vis spectroscopy was used to investigate the interaction between Pb(2+) and 3,4-DHBA at different pH conditions, and FT-IR was used to characterize the precipitate formed during photoreaction. The mineralization of 3,4-DHBA was investigate by total organic carbon analysis.