The degradation of a biologically persistent aminosilicone polymer (PDMAS) formulation, used in the textile industry as a softener of polyester fabrics, was investigated using the Fenton and the photochemically enhanced Fenton reactions. Experiments were performed using a commercially available aqueous silicone formulation (polymer-in-water emulsion stabilized by non-ionic surfactants). Emulsions containing a high PDMAS concentration (typical of textile processing) and a low PDMAS concentration (typical of end-processing wastewater) were investigated. In both cases, treatment by the Fenton and the photo-Fenton processes induced a phase separation after a relatively short reaction time, although the nature of the phase separation was different. Analyses of chemical oxygen demand (COD), nitrate, silicone and iron in the aqueous phase during treatment show that PDMAS (and/or partially oxidized PDMAS) was removed from the aqueous solution as a result of the phase separation process. Reaction pathways and mechanisms are discussed. Focusing on application, the occurrence of a phase separation may be advantageous for textile wastewater treatment, since this would enable the removal of PDMAS by conventional mechanical means. (c) 2004 Published by Elsevier B.V.