Removal of ten pesticides from leaching water at pilot plant scale by photo-Fenton treatment

The protection and remediation of groundwater resources is a priority of EU environmental policy. With this aim, the degradation of ten pesticides in leaching water at pilot plant scale by photo-Fenton treatment under natural sunlight is reported. The solar pilot plant placed in Murcia (SE Spain) is based on compound parabolic collector (CPC) technology. The agrochemicals, commonly used on pepper protection belonging to different chemical groups were azoxyxtrobin, cyprodinil, fludioxonil, kresoxim-methyl, hexaconazole, tebuconazole, triadimenol, and pyrimethanil (fungicides), primicarb (insecticide), and propyzamide (herbicide). All pesticides were found in leachates under laboratory and field conditions although at different rates. Pesticides were added to leaching water (150 L) at 0.5 mg L−1 and the ratio ([Fe2+]/[H2O2]) of Fenton's reagent (FR) at 0.5 was selected. Several samples were taken during the photoperiod (60 min). As expected, the influence of the treatment was very significant in all cases. Photocatalytic experiments show that the addition of FR strongly enhances the degradation rate of the pesticides in comparison with photolytic tests. The disappearance time (DT50) ranged from 2 to 5 min. The first-order equation (monophasic model) ignores small residues remaining late in the dissipation process. These residues are important from an environmental point of view and the Hoerl function (biphasic model) better predict the results obtained.