The photoinduced degradation of an alkylphenol ethoxylate
(APE) (Igepal CA 520) by Fe(III) in aqueous solution has
been investigated. A complete characterization of
the commercial product showed the presence of a mixture
of compounds with various ethoxy and alkyl chain
lengths. The photodegradation study was carried out
with the major fraction of ethoxymers having an alkyl chain
length of 8 carbon atoms and n ethoxy units E (C8PhE
n
).
We have demonstrated that the Fe(III) sensitized degradation
of this fraction occurs efficiently both at 365 nm and
under sunlight. The rate of degradation depends on the
concentration of Fe(OH)2+, the most photoreactive species
in terms of •OH radical formation. The primary step of
the decomposition of Igepal involves the hydrogen abstraction
on one carbon of the ethoxy chain. The shortening of
the ethoxylated chain all along the degradation process
was observed. The identified photoproducts are aldehyde
ethoxylates, formate ethoxylates, and octylphenol that is
a persistent product in the environment. The mechanism
only involves attack by •OH radicals that are formed
through photolysis of Fe(OH)2+. For prolonged irradiations,
the total degradation of Igepal CA 520 and of the
photoproducts is obtained. Consequently, the degradation
photoinduced by Fe(III) could be an efficient method of
APEs removal in water.
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