Kinetics of photocatalytic reduction of Pb(II) on nanocrystalline TiO2 coatings: A quartz crystal microbalance study

Pb(II) is a highly toxic substance, exposure to which can cause various diseases. To better understand the application of TiO2 as a photocatalyst for removing Pb(II) from wastewater, quartz crystal microbalance (QCM) technique was employed to in situ investigate the reduction behavior of Pb(II) on nanocrystalline TiO2 coatings under N2. The processes of Pb(II) reduction at various concentrations of HCOOH and in the presence of different organic additives were monitored, and the corresponding kinetics was proposed. The obtained results showed that the kinetics of Pb(II) reduction on TiO2 coatings was closely related to the organic additives. The HCOOH showed a higher efficiency for Pb(II) reduction in comparison with other organic additives, and the reduction-rate constant reached 0.54 × 10−3 s−1 which was two times higher than that exhibited in the presence of C2H5OH. QCM measurement provides an useful method for monitoring the reduction process of Pb(II) on TiO2 coatings.