Photocatalytic degradation of pesticide-acaricide formetanate in aqueous suspension of TiO2

The photocatalytic degradation of formetanate (FMT) was studied using titan ia Degussa P-25 as a catalyst. The disappearance of formetanate was proved to follow a half-order kinetics. This implies that two active sites are inv olved in the adsorption of one molecule of formetanate (dissociative adsorp tion). In our conditions, complete mineralization of 20 ppm of pure formeta nate occurred within 125 min of UV-radiation. The presence of (i) formulati on agents and (ii) of humic acids seemed to have an inhibiting effect on th e initial rate. In all cases, mineralization of FMT led to a greater percen tage of ammonium than of nitrate. Photocatalysis proved to be an excellent new advanced oxidation technology (AOT) to eliminate formetanate residues p resent in real surface and ground waters. (C) 2001 Elsevier Science B.V. Al l rights reserved.