New photocatalyst for decomposition of humic acids in photocatalysis and photo-Fenton processes

Humic acid Leonardite IHSS standard was decomposed on TiO₂ and TiO₂ modified by FeC₂O₄ via the photocatalysis and photo-Fenton processes under UV irradiation. Humic acid (HA) were favorable adsorbed on TiO₂ surface and followed decomposition during UV irradiation faster on TiO₂ than on the modified samples. However, when H₂O₂ was added to the solution, the photo-Fenton process occurred on the prepared TiO₂ samples, contained iron together with photocatalysis and high acceleration of HA decomposition was observed. In this case the mineralization degree was much higher than in the applied photocatalysis only, around 75% HA (with concentration of 18 mg/L) was mineralized after 3 h of adsorption and 5 h of UV irradiation in the presence of H₂O₂ and modified TiO₂ whereas on TiO₂ mineralisation of HA occurred in around 45% only. The measured fluorescence spectra of HA solutions showed that in the presence of H₂O₂ polycyclic aromatics were rapidly oxidized to the lower size products such as alcohols, aldehydes, ketones and carboxylic acids, what accelerated the process of HA decomposition.