Photooxidation of exhaust pollutants IV. Photocatalytic and thermal decomposition of trichloroacetic acid: degradation efficiencies and products

The photocatalytical and thermal decomposition as well as the oxidation of trichloroacetic acid (TCA) was investigated in the aqueous phase by irradiation with a low pressure mercury lamp in the presence of titanium dioxide (TiO2). In addition, the thermal decomposition without irradiation was examined in dependence of pH, temperature and oxidizing agents. In all experiments TCA was mineralized and decomposed totally with chloride as main product. Chloroform could be identified in traces by GC-MS. Heating to 90° C in alkaline solution is the fastest way to destroy TCA. At high temperatures the half-life is recognizably larger at photocatalytical decomposition and could almost not be influenced by change of reaction terms. Degradation products of TCA, their kinetics and mechanism of formation are discussed in detail.