| This dissertation describes the photocatalytic reaction pathways undergone by metal and metalloid ions (As, Pb, and Zn) in UV-irradiated TiO2 suspensions. Thermodynamic considerations show that these species can participate in both electron-mediated (reductive) as well as hole-mediated (oxidative) photoreaction pathways. Experimental data are presented in verification of these expectations in various scenarios including: platinization of the TiO 2 surface, the ambient atmosphere (whether O2 or N2 ), and the presence of co-added organic substrates such as aliphatic alcohols, formate or acetate ions. An electron acceptor (e.g., O2) is needed for the hole transfer pathway where the heterogeneous photocatalytic reduction is facilitated by hole scavengers such as alcohols. Even counterions for the metal ions (e.g., nitrate) can play an important role in the reductive reaction pathway. |
