W. Baran, E. Adamek, K. Wiśniewska, M. Cholewiński
Medical University of Silesia in Katowice, Katowice, PL

A STUDY ON INITIATION OF PHOTOCATALYTIC DEGRADATION OF SULFADRUGS IN THE TiO2/FeCl3 SYSTEM


A photocatalytic process conducted in the presence of TiO2/FeCl3 mixture is one of the most effective methods to degrade of pharmaceuticals, including sulfonamides, from an aquatic environment. However, its kinetics depends largely on the type of degraded substrate. The objective of the study was to assess the effect of pH, aerobic conditions and selective inhibitors of the photocatalytic process on the kinetics of degradation of the selected sulfonamides (sulfanilamide, sulfathiazole, sulfafurazole and sulfadiazine). The photocatalytic process was initiated by UVA irradiation in the presence of catalytic system composed of TiO2-P25 (Aeroxide®) suspension and a FeCl3 solution. Under anaerobic conditions, the experiment was conducted in an argon atmosphere and methanol and t-butanole was used as selective inhibitors It was stated that photocatalytic degradation of sulfafurazole proceeded according to the different mechanism than in other three sulfonamides. Sulfafurazole was degraded mainly by O2•-radicals. Contrary, sulfanilamide, sulfathiazole and sulfadiazine degradation was limited mainly by availabiltity of photogenerated holes on the catalyst surface. Additionally, in each case, the presence of [Fe(OH)(H2O) 5]2+ ions was important for the efficiency of sulfonamides degradation.

Keywords: mechanism, photocatalysis, sulfonamides, radicals.