TiO2-Based Heterogeneous Photocatalytic Water Treatment Combined with Ozonation

The degradations of aliphatic carboxylic acids (formic acid, acetic acid, and propionic acid) were investigated by a combination of TiO₂-based photocatalysis and ozonation at pH = 2. The carboxylic acids were analyzed by high-performance liquid chromatography (HPLC), while the mineralization process was characterized by measuring the dissolved organic carbon (DOC) content. The efficiency of heterogeneous photocatalysis combined with ozonation was compared with that of ozonation and that of heterogeneous photocatalysis alone. In all cases, the combined system proved most effective in the oxidation of carboxylic acids. The degradation of carboxylic acids was accompanied by a continuous decrease in the DOC content, and aldehydes and carboxylic acids containing one carbon atom less than the starting material were formed as intermediates.