Photocatalytic degradation of the herbicide quinclorac in water using Mn (III) salen and solar light

Abstract

Quinclorac (QNC) is a widely used herbicide and is persistent in surface and ground waters. Its residualsand converted products are hazardous to aquatic animals, vegetation, and microbes, and it is therefore important todegrade QNC using an efficient and environmental friendly technology. In this study, the photocatalytical degradationof QNC using [(R,R)-(N,N′-bis(3,5,3′,5′-tetra-tert-butylsalicylidene)-1,2-cyclohexanediaminato] manganese(III) acetate(Mn (III) salen) and H2 O2 was performed under natural sunlight irradiation and a 91% degradation rate was achievedin neutral pure water in 240 min. The identified degradation products confirmed that the cleavage of QNC moleculeswas the main process involved in the hydroxylation, along with the cracking of the N=C bond on the pyridine ringand hydroxylation on the benzoic ring. The active species analysis showed hydroxyl radicals and superoxide radicalswere the main reactive species. Photocatalytic kinetics indicated that the degradation process was in accordance with apseudo-first-order kinetic equation.