Reaction of Amino Acids with Ferrate(VI): Impact of the Carboxylic Group on the Primary Amine Oxidation Kinetics and Mechanism

Abstract

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.

How Should We Activate Ferrate(VI)? Fe(IV) and Fe(V) Tell Different Stories about Fluoroquinolone Transformation and Toxicity Changes

“…Fe­(VI)-based advanced oxidation processes may involve active species such as Fe­(IV), Fe­(V), O 2 , H 2 O 2 , OH·, and O 2 ·– through self-decomposition of Fe­(VI) in aqueous solution. , Moreover, CO 3 ·– might be produced in the NaHCO 3 /Fe­(VI) process. PMSO was used as a probe to investigate the active species. , Fe­(IV)/Fe­(V) converts PMSO to PMSO 2 , whereas other active species cause PMSO to form polymeric and/or hydroxylated products but not PMSO 2 . As shown in Figure a and Figure S4 (Fe­(VI) alone), all the PMSO was transformed into PMSO 2 , which demonstrated that Fe­(IV)/Fe­(V) were the only reactive species in the three processes.…”

“…PMSO was used as a probe to investigate the active species. 37,38 Fe(IV)/Fe(V) converts PMSO to PMSO 2 , whereas other active species cause PMSO to form polymeric and/or hydroxylated products but not PMSO 2 . 39 As shown in Figure 2a and Figure S4 (Fe(VI) alone), all the PMSO was transformed into PMSO 2 , which demonstrated that Fe(IV)/ Fe(V) were the only reactive species in the three processes.…”

Elucidation of the Photochemical Fate of Methionine in the Presence of Surrogate and Standard Dissolved Organic Matter under Sunlight Irradiation

“…The peroxyl radical produced from the addition of O 2 to the C-centered radical undergoes O 2 •– elimination followed by the formation of imine , and carbinolamine that then undergoes deammonification to simultaneously produce NH 4 + and methional (Figure ). – …”

Revisiting the Electron Transfer Mechanisms in Ru(III)-Mediated Advanced Oxidation Processes with Peroxyacids and Ferrate(VI)

“…Compared with radicals, high-valent metals generally have a higher steady-state concentration and better selectivity toward micropollutants due to targeting their electron-rich moieties. − Furthermore, high-valent metal species may resist the influence of matrices in the treatment of real water samples. High-valent iron (Fe­(IV)/Fe­(V), ferrate­(VI) (Fe VI O 4 2– )) species usually selectively react with contaminants with phenolic, − nitrogen-containing, − or sulfur-containing functional groups , while exhibit low reactivity toward merely aliphatic or aromatic compounds. For instance, benzoic acid, a commonly used probe compound and typical structure in natural organic matter, is inert to high-valent iron but susceptible to oxidation by nonmetallic radicals, including HO • , SO 4 •– , and Cl • . ,, In addition, unlike radicals susceptible to scavenging by halides, , ferrate­(VI) exhibits relatively low reactivity to bromide and almost no reactivity to chloride, hence mitigating the formation of toxic halogenated byproducts. ,− …”