Differentiation of Pathways of Nitrated Byproduct Formation from Ammonium and Nitrite During Sulfate Radical Oxidation

Recent studies found that both nitrite (NO2-) and ammonium (NH4+) lead to nitrophenolic byproducts in SO4 center dot- oxidation processes, during which NO2 center dot generated through the oxidation of the inorganic nitrogen by SO4 center dot- is the key nitrating agent. This study demonstrates that the formation of phenoxy radicals to which NO2 center dot can be incorporated immediately is another governing factor. Two types of sites having distinct reactivities in natural organic matter (NOM) molecules can be transformed to phenoxy radicals upon SO4 center dot- oxidation. Fast sites associated with phenolic functionalities are primarily targeted in the reaction sequence involving NO2-, because both are preferentially oxidized. Following the depletion of NO2-, NH4+ becomes the main precursor of NO(2)(center dot )that interacts with slow sites associated with the carboxylic functionalities. Experimental data show that the formation of total organic nitrogen in 24 h reached 6.28 mu M during SO4 center dot- oxidation of NOM (4.96 mg/L organic carbon) in the presence of both NO2- (0.1 mM) and NH4+ (1.0 ), while the sum of those formed in the presence of each alone was only 3.52 mu M. Results of this study provide further insights into the mechanisms of nitrated byproduct formation when SO4 center dot- is applied for environmental remediation.

Automated summary

Recent studies have found that nitrite and ammonium can lead to the formation of nitrophenolic byproducts during SO4 center dot- oxidation processes. This study provides further insights into the mechanisms of nitrated byproduct formation.