title: Photocatalytic degradation of eight pesticides in leaching water by use of ZnO under natural sunlight.
abstract: Photodegradation of eight pesticides in leaching water at pilot plant scale using the tandem ZnO/Na(2)S(2)O(8) as photosensitizer/oxidant and compound parabolic collectors under natural sunlight is reported. The pesticides, habitually used on pepper culture and belonging to different chemical groups were azoxyxtrobin, kresoxim-methyl, hexaconazole, tebuconazole, triadimenol, and pyrimethanil (fungicides), primicarb (insecticide), and propyzamide (herbicide). As expected, the influence of the semiconductor used at 150 mg L(-1) on the degradation of pesticides was very significant in all cases. Photocatalytic experiments show that the addition of photosensitizer strongly improves the elimination of pesticides in comparison with photolytic tests; significantly increasing the reaction rates. The use of Na(2)S(2)O(8) implies a significant reduction in treatment time showing a quicker reaction time than ZnO alone. On the contrary, the addition of H(2)O(2) into illuminated ZnO suspensions does not improve the rate of photooxidation. The disappearance of the pesticides followed first-order kinetics according to Langmuir-Hinshelwood model and complete degradation occurs from 60 to 120 min. The disappearance time (DT(75)), referred to the normalized illumination time (t(30 W)) was lower than 3 min in all cases.
authors.affiliation: Departamento de Química Agrícola, Geología y Edafología. Facultad de Química, Universidad de Murcia, Murcia, Spain. snavarro@um.es
authors.forename: S
authors.initials: S
authors.lastname: Navarro
authors.forename: J
authors.initials: J
authors.lastname: Fenoll
authors.forename: N
authors.initials: N
authors.lastname: Vela
authors.forename: E
authors.initials: E
authors.lastname: Ruiz
authors.forename: G
authors.initials: G
authors.lastname: Navarro
mesh_terms: D005659:Fungicides, Industrial; D006540:Herbicides; D006861:Hydrogen Peroxide; D007306:Insecticides; D007700:Kinetics; D010575:Pesticides / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects; D018508:Water Purification / Q000379:methods; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D005659:Fungicides, Industrial; D006540:Herbicides; D007306:Insecticides; D010575:Pesticides; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; D015034:Zinc Oxide