LAUSR

Abstract The efficiency of TiO2 based heterogeneous photocatalysis can be enhanced by its combination with other oxidative procedures such as ozonation and by the modification of the catalyst surface with noble metals (such as silver). In this work, degradation of 4-hydroxybenzenesulfonic acid (4-HBS, a key intermediate of the decomposition of benzenesulfonic acid) was thoroughly studied by application of the above mentioned procedures individually and also in various combinations. Detailed comparisons of these methods were realized by measurements of degradation and mineralization of 4-HBS as well as determination of characteristic hydroxy intermediates and sulfate ions. The degradation efficiency of combination of Ag-TiO2 based photocatalysis and ozonation was just about the sum of the efficiencies of the individual procedures, while mineralization efficacy of this combination proved to be highly synergic, considerably exceeding this feature of the air- Ag-TiO2 system, due to the increased rate of ozone decay producing ring-opening radicals. Accordingly, total mineralization of 4-HBS was realized under these conditions. Ozonation, however, caused an oxidative dissolution of the deposited silver from the surface of the catalyst. Even so, simultaneous application of Ag-TiO2 based heterogeneous photocatalysis and ozonation led to total mineralization faster than their consecutive combination did.