Photosensitized degradation in water of the phenolic pesticides bromoxynil and dichlorophen in the presence of riboflavin, as a model of their natural photodecomposition in the environment.
Within the context of environmentally friendly methods for the elimination of surface-water pollutants, the photodegradation of the phenolic pesticides bromoxynil (BXN) and dichlorophen (DCP) under simulated natural conditions has been studied. The work was done in the presence of the visible-light absorber photosensitizer riboflavin (Rf), usually present in trace quantities in natural waters. Under aerobic conditions, an efficient photooxidation of both pesticides was observed. The relatively intricate photochemical mechanism involves pesticide and oxygen consumption and, to a lesser extent, Rf degradation. The kinetic and mechanistic study supports that both H(2)O(2) and singlet molecular oxygen, O(2)((1)Δ(g)), are involved in the process. Kinetic data for the O(2)((1)Δ(g))-mediated oxidation indicate that BXN and DCP are photodegraded with this species faster than the parent compound phenol, very frequently employed as a model for aquatic contaminants, likely due to their lower pK(a) values. This observation allows the design of phenolic pesticides with different photodegradation rates under environmental conditions.
Unidad Académica Río Gallegos, Universidad Nacional de la Patagonia Austral, Río Gallegos, Argentina.
Juan P
JP
Escalada
Adriana
A
Pajares
José
J
Gianotti
Alicia
A
Biasutti
Susana
S
Criado
Patricia
P
Molina
Walter
W
Massad
Francisco
F
Amat-Guerri
Norman A
NA
García
D004003:Dichlorophen / Q000737:chemistry*; D007700:Kinetics; D009570:Nitriles / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D010575:Pesticides / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D010777:Photochemistry; D013057:Spectrum Analysis / Q000379:methods
D009570:Nitriles; D010575:Pesticides; D010636:Phenols; C006826:bromoxynil; D010100:Oxygen; D004003:Dichlorophen