Photochemical degradation of triazine herbicides - comparison of homogeneous and heterogeneous photocatalysis.
Photochemical degradation of atrazine under different conditions was studied and compared, namely degradation via photocatalysis on TiO2, UV C photolysis, and homogeneous photocatalysis in the presence of added ferric ions. The reaction rate constants in heterogeneous photocatalytic reactions on TiO2 and of photolytic degradation by means of UV C light are similar, 0.018 min(-1) and 0.020 min(-1), respectively. The reaction rate constants in homogeneous photocatalytic reactions with Fe(III) added depend strongly on the Fe(III) concentration, 0.0017 min(-1) for 1.6 × 10(-6) mol l(-1) Fe(III) to 0.105 min(-1) for 3.3 × 10(-4) mol l(-1) Fe(III). In all types of reactions, dechlorination was observed; in homogeneous photocatalytic reactions and in UV C (250-300 nm) photolysis, dechlorination proceeds with a 1 : 1 stoichiometry to atrazine degradation, in photocatalytic reactions on TiO2, dechlorination measured as chloride ion release reaches only 1/5 of the substrate degradation. In photocatalytic reactions on TiO2, mineralisation of 40% carbon was observed.
Faculty of Science, University of South Bohemia, Branisovská 31, 370 05 Ceske Budejovice, Czech Republic. sklement@jcu.cz
Sarka
S
Klementova
Martin
M
Zlamal
D001280:Atrazine / Q000737:chemistry* / Q000528:radiation effects; D002384:Catalysis; D002712:Chlorides / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays
D002712:Chlorides; D005290:Ferric Compounds; D006540:Herbicides; C009495:titanium dioxide; D014025:Titanium; D001280:Atrazine