In this thesis, I studied the influence of different water matrices on the photocatalytic degradation of a mixture of five pharmaceuticals with TiO$_2$ thin films deposited on glass plates. I performed photocatalytic degradation tests for two hours under UV-light, and the concentrations of individual compounds were monitored by high-performance liquid chromatography (HPLC). The results showed that the degradation rate strongly depends on both the chemical structure of the pharmaceutical and the composition of the aqueous matrix. Diclofenac and naproxen degraded the fastest, while sulfamethoxazole and phenytoin proved to be the most persistent in most cases. The effect of the aqueous matrix showed a nonlinear response to ionic strength and the presence of natural organic matter (NOM), with these two effects inhibiting the degradation under some conditions and accelerating it under others. The findings show that the results of photocatalytic degradation in simple laboratory solutions do not always reflect real behaviour in natural aquatic environments, therefore, it is essential to consider the specific properties of the water matrix and pollutants when planning wastewater treatment processes.
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