Photocatalytic reduction of divalent zinc and cadmium ions in aqueous TiO2 suspensions: an interfacial induced adsorption¯reduction pathway mediated by formate ions

A new pathway is described for the photocatalytic reduction of metal ions in organicloaded aqueous TiO2 suspensions. Thus, formate ions act as interfacial anchors to initially sequester Zn(II) and Cd(II) ions onto the TiO2 particle surfaces. Subsequent UV illumination of the suspensions results in the facile photoreduction of these metal ions. In the absence of formate, the metal ions show little proclivity either to adsorb on the TiO2 particle surfaces or to undergo photoreduction.