Reactivity of nitrogen species with inorganic and organic compounds in water

Many studies on the reactive nitrogen species (RNS, ^●NO₂, ^●NO and ^●NH₂) with pollutants in water have been performed to understand the abatement of inorganic and organic compounds by these species, and the mechanisms of the formation of oxidative transformation products, especially nitrogenous oxidized byproducts. In this review, approaches to generate RNS in aqueous solution is first presented, followed by a summary of their reactivity with a wide range of compounds. The second-order rate constants (k, M^-1 s^-1) for the reactivity of ^●NO₂ and ^●NO with a wide range of inorganic radical and nonradical species were correlated with thermodynamic one-electron oxidation potentials (E⁰). The positive correlation between log(k) versus E⁰ suggests one-electron transfer reactions. The Hammett-type correlations were developed for the reactions of ^●NO₂ and ^●NH₂ with organic compounds, using the unsubstituted benzene as a reference molecule (i.e., Σσ_o,p,m = 0) to calculate Σσ_o,p,m = σ_o + σ_p + σ_m for each organic molecule. Linear negative correlations of log(k) with Σσ_o,p,m were obtained for both ^●NO₂ and ^●NH₂, suggesting electrophilic substitution mechanism. The correlations presented herein may assist in eliminating organic micropollutants in water treatment and reuse processes.