Photodechlorination Mechanism of DDT in a UV/Surfactant System

The photochemical reactions of the organochlorine pesticide DDT in aqueous solutions containing nonionic surfactant micelles (Brij 35, Brij 52, and Brij 72) were investigated and modeled. All photolytic experiments were conducted in a Rayonet RPR-200 merry-go-round photoreactor using a 253.7-nm mercury monochromatic ultraviolet (UV) lamps. Pseudo-first-order decay through photodechlorination was observed to be the dominant reaction pathway for DDT photodecay. The primary photoproducts include lesser chlorinated compounds (DDE and DDD) and hydrogen chloride. The photodechlorination of DDT involves two stages; the first is the fast aliphatic chlorine reduction, followed by a slow aromatic chlorine reduction. The photodecay rates of DDT were doubled in the Brij 52 micellar solution compared to that in water alone. A first-order parallel/consecutive model was developed and found useful to predict the photodecay of DDT and the generation of DDE/DDD in the micellar/aqueous system.