Photocatalytic degradation of the herbicide “Paraquat”

The photocatalytic degradation of pure paraquat ( 1,1′-dimethyl-4,4′-bipyridinium dichloride ) aqueous solutions with UV light over titanium oxide was investigated. Experimental results have confirmed that paraquat is slowly degraded by direct photolysis in the presence of dissolved oxygen. Addition of TiO2 to the reaction system substantially increases the initial rate of reaction and the overall conversion of paraquat. Complete photocatalytic degradation of paraquat at high pH values was found to occur in less than three hours of reaction.