During drinking water treatment reactions, the physicochemical properties of organic species are important, i.e. their tendency to adsorb onto particles and partition into hydrophobic portions of natural organic matter (NOM). This is especially true of permanganate oxidations, which generate hydrous manganese(III,IV) oxide (HMO) particles in suspension. HMO particles can oxidize organic functional groups that are relatively unreactive towards permanganate. Here, we focus on hydroxycarboxylic acids and their products of permanganate oxidation that are subject to hydration reactions and keto-enol tautomerization: the keto acids and aldehydes. These compound classes are present within NOM, and are also found within the structures of cyanobacterial toxins, pharmaceuticals, and personal care products. Mandelic acid and phenyllactic acid provide an interesting comparison. The latter contains a methylene linkage that electronically isolates the benzene ring from the hydroxycarboxylic acid group. As a consequence, oxidation pathways and product yields are altered. Electron donating and withdrawing substituents, along with changes in medium composition (e.g. pH, presence of Fe(II) and Mn(II)) alter oxidation pathways and rates. To account for these effects, it is necessary to account for adsorption affinity toward HMO particles and other physicochemical properties.

Heterogeneous nature of permanganate oxidation reactions

249th National Meeting (2015)

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