Heterogeneous photocatalytic reduction of As(V) and As(III) at different concentrations over TiO(2) under UV light in deoxygenated aqueous suspensions is described. For the first time, As(0) was unambiguously identified together with arsine (AsH(3)) as reaction products. As(V) reduction requires the presence of an electron donor (methanol in the present case) and takes place through the hydroxymethyl radical formed from methanol oxidation by holes or hydroxyl radicals. On the contrary, As(III) reduction takes place through direct reduction by the TiO(2)-conduction band electrons. Detailed mechanisms for the photocatalytic processes are proposed. Although reduction to solid As(0) is convenient for purposes of As removal from water as a deposit on TiO(2), attention must be paid to formation of AsH(3), one of the most toxic forms of As, and strategies for AsH(3) treatment should be considered.

Experiments to evaluate the photocatalytic activity of supported TiO2 to potabilize water in common plastic PET bottles under solar irradiation were performed. Commercial titanium dioxide (Degussa P-25) was applied to different cheap materials—glass rings, glass rods and porcelain beads—by dip coating, or directly to the plastic wall of the bottles. The adherence and stability of TiO2 on the supports and the photocatalytic activity in bottles under solar irradiation was evaluated using model compounds as 4-chlorophenol and 2,4-dichlorophenoxyacetic acid. Rings were found to be the best glass supports, but PET bottles were superior for this specific application, as no fragile fillings are used, and the materials can be easily fabricated on site.