Polyoxometalate anions (POM), resulting from the condensation of tungstate anions in strongly
acidified solutions, can absorb efficiently light in the UV-near Vis region.The produced excited state is a very
powerful oxidative reagent which can, mainly via OH radical attack, oxidize and mineralize a great variety
of organic pollutants in aqueous solutions, while the photocatalytic circle is closed by reoxidation of the
reduced POM, mainly, by O2. Metal ions can also serve as oxidants and close the photocatalytic cycle. In the
process metal ions are reduced, precipitated and removed from the solution. Thus photocatalytic treatment
for decontamination of waste waters from both organic and inorganic pollutants (metal ions) can be, in
principle, achieved. POM+S→hνPOMred+SoxPOMred+Mn+→POM+Mred
Atrazine, a widely used herbicide with s-triazine structure, is photodecomposed to cyanuric acid in presence
of SiW12O404-
in aqueous solutions. However, no precipitation of metal ions is obtained when atrazine is the
sole organic substrate in aqueous solutions. The low solubility of atrazine produces insufficient concentration
of reduced POM to cause precipitation.
