Photochemical degradation of triazine herbicides - Comparison of homogeneous and heterogeneous photocatalysis

Abstract

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 TiO 2, 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. © The Royal Society of Chemistry and Owner Societies 2013.