Nonionic detergent degradation: III. Initial mechanism of the degradation

In Parts I and II of this series (1,2), degradation and foaming experiments on a number of commercially available alcohol polyethoxylates and alkyl phenol polyethoxylates are described. This paper describes an extension of the thin layer chromatographic work on which the experiments described earlier were based, supplemented by a variety of other chemical and physical tests to provide some insight into the initial mechanism of degradation of these materials before they disappear by the established oxidation and hydrolytic routes. In the case of the readily degradable alcohol ethoxylates, two distinct mechanisms are shown to proceed simultaneously: a fission of the molecule into hydrophobic and hydrophilic entities, and a rapid oxidation of the hydrophobic group. No fission occurs in the case of the alkyl phenol ethoxylates, the more usual route of degradation being slow oxidation and hydrolysis of the alkyl groups, the aromatic ring and the ethoxy chain simultaneously; occasionally, and at higher pH, the hydrolysis of the ethoxy chain proceeds at a considerably increased rate.