Synergetic denitrification through co-removal of nitro and amino/N-heterocyclic compounds in supercritical water

Abstract

Supercritical water oxidation (SCWO) of 20 N-containing mixtures was investigated under 24 MPa, 450 °C and reaction time from 0.5 min to 6 min, with initial concentration of 1 mM. TN removal of the mixtures obtained a sharp improvement as reaction time increased from 0.5 min to 3 min, the TN removal efficiencies was over 50% at 6 min. The TN degradation rate of the mixture (kM-TN) was higher than that of the initial nitro, amino or N-heterocyclic compound. Interestingly, kM-TN was largely affected by the TOC degradation rates (kTOC) of the initial N-containing compounds, which implied that the nitro and amino/N-heterocyclic compounds, containing similar kTOC, would lead to a high value of kM-TN after mixing. Distribution of N-containing products showed that org-N made a main contribution to the formation of N2. Molecular descriptors, like EHOMO, ELUMO and q N, largely influenced kM-TN.