Oxidation of N-nitrosodimethylamine in a heterogeneous nanoscale zero-valent iron/H2O2Fenton-like system: influencing factors and degradation pathway

Abstract

BACKGROUND N-nitrosodimethylamine (NDMA) is an emerging disinfection byproduct, which is also classified as a potential carcinogen and mutagen. Advanced oxidation processes based on hydroxyl radical (•OH) have been suggested as an effective NDMA elimination method. This study focused on investigating the mechanism of oxidative degradation of NDMA using a nanoscale zero-valent iron (nZVI) induced heterogeneous Fenton system. RESULTS The results show that nZVI was stable in the system. NDMA (≤1 mg L−1) was completely removed in 60 min under the following optimal conditions: initial pH =3.0, H2O2 concentration =2 mmol L−1 and nZVI dose =56 mg L−1. Major dissolved species (such as HCO3−, Cl− and humic acid) in a natural water matrix reduced the degradation rate of NDMA. During the degradation of NDMA, eight degradation intermediates were detected and confirmed, including methylamine (MA), dimethylamine (DMA), ammonia (AM), nitromethane (NM), hydroxyurea (HU), acetaldehyde (AA), NO2− and NO3−. Based on the identified intermediates, a tentative degradation pathway of NDMA in the nZVI/H2O2 system was proposed. CONCLUSION Results indicate that nZVI as the catalyst used in the heterogeneous Fenton system is an effective alternative to remove NDMA. © 2016 Society of Chemical Industry