Enhanced photocatalytic reduction of aqueous Pb(II) over Ag loaded TiO₂ with formic acid as hole scavenger

Abstract

In the present study, photocatalytic Pb(II) reduction over TiO₂ and Ag/TiO₂ catalysts in the presence of formic acid was explored to eliminate Pb(II) pollution in water. Ag/TiO₂ catalysts were prepared by the photo-deposition method and characterized using UV-Vis diffuse reflectance spectra, X-ray reflection diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Ag deposition on TiO₂ led to enhanced photocatalytic Pb(II) reduction and the Ag/TiO₂ catalyst with a Ag loading amount of 0.99 wt.% exhibited the optimum photocatalytic activity. For Pb(II) reduction over Ag/TiO₂ with a Ag loading amount of 0.99 wt.%, initial Pb(II) reduction rate was found to be dependent on the initial concentrations of formic acid and Pb(II). Increasing initial Pb(II) concentration led to linearly increased initial Pb(II) reduction rate. At low formic acid concentration, in parallel, initial Pb(II) reduction rates increased with formic concentration, but remained nearly identical at high formic acid concentration. Solution pH impacted the photocatalytic Pb(II) reduction and after irradiation for 100 min Pb(II) was removed by 11.8%, 91.2% and 98.6% at pH of 0.8, 2.0 and 3.5, respectively, indicative of enhanced Pb(II) reduction with pH in the tested pH range. The results showed that Ag/TiO₂ displayed superior catalytic activity to TiO₂, highlighting the potential of using Ag/TiO₂ as a more effective catalyst for photocatalytic Pb(II) reduction.

Keywords:

• Photocatalytic Pb(II) reduction
• Ag/TiO₂ catalyst
• formic acid
• hole scavenger

Acknowledgments

The financial supports from the Natural Science Foundation of China (No. 20807023 and 20877039), Important National Science & Technology Specific Project (2008ZX07421-006) and Program of New Century Excellent Talents in University (NCET-08-0277) are gratefully acknowledged.