Surfactant-assisted removal of swep residues from soil and photocatalytic treatment of the washing wastes

The photocatalytic treatment of soil washing wastes containing the pesticide swep and three different surfactants: sodium dodecylsulfate (SDS), hexadecyltrimethylammonium bromide (HTAB) and polyoxyethylene(8) dodecyl ether (C12E8), has been investigated. Better extraction performances of swep (methyl-N-(3,4-dichlorophenyl)carbamate) from contaminated soil samples have been obtained using aqueous SDS solutions. The pesticide abatement in the wastes, performed by photocatalysis in the presence of irradiated TiO2 dispersions, was faster in the presence of SDS and slower in the presence of HTAB, whereas a marked degradation inhibition was observed when C12E8 solutions were used. The monitoring of end products formation in water, together with a detailed MS examination of the transient intermediates formed during the earlier steps of the pesticide degradation, allowed to give insight into the process mechanism operating in aqueous media.