Photocatalytic degradation of herbicide fluroxypyr in aqueous suspension of TiO2

The photocatalytic degradation of fluroxypyr (FLX) was studied using Degussa P-25 Titania as a catalyst. The disappearance of FLX was proved to follow a half-order kinetics. This implies that two active sites are involved in the adsorption of one molecule of fluroxypyr. In our conditions, complete mineralization of 40 ppm of pure fluroxypyr occurred within ca. 240 min of UV-radiation. Some reaction intermediates were identified by HPLC–MS (ESI+) and a tentative degradation pathway was proposed. The presence of HCl (pH 2) seemed to have an inhibiting effect on the initial rate, whereas degradation of FLX was accelerated at basic pH values (pH 8 or 10, achieved with CaCO3 or NaOH, respectively). Photocatalysis proved to be an excellent new advanced oxidation technology (AOT) to eliminate fluroxypyr residues present in surface and ground waters.