Ferrate
(Fe(VI)) is a novel oxidant that can be used
to mitigate
disinfection byproduct (DBP) precursors. However, the reaction of
Fe(VI) with organic nitrogen, which is a potential precursor of potent
nitrogenous DBPs, remains largely unexplored. The present work aimed
to identify the kinetics and products for the reaction of Fe(VI) with
primary amines, notably amino acids. A new kinetic model involving
ionizable intermediates was proposed and can describe the unusual
pH effect on the Fe(VI) reactivity toward primary amines and amino
acids. The Fe(VI) oxidation of phenylalanine produced a mixture of
nitrile, nitrite/nitrate, amide, and ammonia, while nitroalkane was
an additional product in the case of glycine. The product distribution
for amino acids significantly differed from that of uncarboxylated
primary amines that mainly generate nitriles. A general reaction pathway
for primary amines and amino acids was proposed and notably involved
the formation of imines, the degradation of which was affected by
the presence of a carboxylic group. In comparison, ozonation led to
higher yields of nitroalkanes that could be readily converted to potent
halonitroalkanes during chlor(am)ination. Based on
this study, Fe(VI) can effectively mitigate primary amine-based, nitrogenous
DBP precursors with little formation of toxic halonitroalkanes.
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