Oxidation of reduced daughter products from 2,4-dinitroanisole (DNAN) by Mn(Ⅳ) and Fe(Ⅲ) oxides

摘要

Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminant fate in soil. The capacity of bimessite and ferrihydrite to oxidize the insensitive munitions compound, 2,4-dinitroanisol (DNAN), and its amine-containing daughter products, 2-methoxy-5-nitro aniline (MENA) and 2,4-diaminoanisole (DAAN), was studied in stirred reactors at controlled pH (7.0). Aqueous suspensions were reacted at metal oxide solid to solution mass ratios (SSR) of 0.15, 1.5 and 15 g kg(-1) and solutions were analyzed after 0-3 h by high performance liquid chromatography coupled with photo diode array or mass spectrometry detection. Results indicate that DNAN was resistant to oxidation by bimessite and ferrihydrite. Ferrihydrite did not oxidize MENA, but MENA was susceptible to rapid oxidation by birnessite, with nitrogen largely mineralized to nitrite. This is the first report on mineralization of nonphenolic aromatics and the release of mineralized N from aromatic amines following reaction with birnessite. DAAN was oxidized by both solids, but ca. ten times higher rate was observed with bimessite as compared to ferrihydrite at an SSR of 1.5 gkri. At 15 gkri SSR, DAAN was removed from solution within 5 min of reaction with bimessite. CO2(g) evolution experiments indicate mineralization of 15 and 12% of the carbon associated with MENA and DAAN, respectively, under oxic conditions with birnessite at SSR of 15 g kg(-1). The results taken as a whole indicate that initial reductive (bio)transformation products of DNAN are readily oxidized by bimessite. The oxidizability of the reduced DNAN products was increased with progressive (bio)reduction as reflected by impacts on the oxidation rate. (C) 2018 Elsevier Ltd. All rights reserved.