The photocatalytic mineralisation of sucrose, used here as a model organic compound, was investigated in the presence of dissolved copper(II) ions using Degussa P25 titanium dioxide as the photocatalyst. The copper ions were found to substantially enhance the photocatalytic mineralisation rates. The photocatalytic activity increased until an optimum metal concentration was reached. Beyond which, the activity first dropped slightly and then remained constant for the range of Cu(II) ion concentrations studied. At pH 3.5, with the optimum Cu(II) concentration of 2 at.%, a three-fold increase was observed in the maximum mineralisation rate. At pH 1.5, an approximately eight-fold increase was found in the mineralisation rate of sucrose, although the overall reaction rate was found to be lower than at pH 3.5. The copper ions showed little adsorption onto the TiO 2 surface. This is strong evidence to suggest that the enhancement of the photocatalytic mineralisation rate had occurred through a homogeneous pathway mechanism.
The findings of this study are important when considering the effects which inorganic ions commonly found in contaminated waters, such as copper(II), have on the photocatalytic degradation of organics.