Synergetic removal of Pb(II) and dibutyl phthalate mixed pollutants on Bi2O3-TiO2 composite photocatalyst under visible light

A highly efficient Bi2O3-TiO2 composite, prepared by a facile hydrothermal method, can be used for the removal of heavy metal Pb(II) and refractory organic dibutyl phthalate (DBP) from wastewater under visible light irradiation. The photo-induced electrons and holes separately transfer to different locations on the composite, resulting in different photocatalytic reaction sites for the refractory organic oxidation and the heavy metal reduction. This separation in space, thereby greatly improves the photocatalytic efficiency of both reactions. The energy level adjustment caused by Fermi levels matching at the n-p heterojunction, resulted in the Pb(II) being reduced to Pb(0) on the Bi2O3-TiO2 composite in visible light in both the Pb(II)-only and Pb(II)-DBP mixed systems. In contrast, no reduction was observed in visible light using only a Bi2O3 or TiO2 catalyst. Furthermore, the presence of refractory organic DBP in the system significantly increased the removal of Pb(II) while the presence of the more easily degradable phenol increased it to a lesser extent. These results indicate that coupling the reduction rate of heavy metals and the oxidation rate of organics can efficiently enhance the photocatalytic activity of the entire system.