The degradation of 3,4-dihydroxybenzoic acid (3,4-DHBA) in the presence and absence of Pb2+ under UV illumination was studied. Addition of Pb2+ caused the formation of precipitate during photoreaction when the solution pH was higher than 6. The presence of Pb2+ remarkably inhibited the degradation of 3,4-DHBA and its photodegradation intermediates, while complexation of 3,4-DHBA and its photodegradation intermediates with Pb2+ decreased the free Pb2+ in aqueous solutions. Molecular oxygen played an important role in photodegradation of 3,4-DHBA in the presence of Pb2+. UV–Vis spectroscopy was used to investigate the interaction between Pb2+ 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.
Keywords: 3,4-dihydroxybenzoic acid, Pb2+ complex, photodegradation, precipitate