Electro-assisted Fenton treatment of ammunition wastewater containing nitramine explosives

The treatment of an actual wastewater from ammunition manufacturing process containing highly hazardous nitramine explosives has been studied by different water treatment technologies based on Fenton's chemistry. The in-situ production of hydroxyl radical as highly oxidizing agent conducted to the overall degradation of the nitramine explosives contained in the effluent samples. The kinetic abatement of octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) followed the crescent order Fenton = photo-Fenton > electro-assisted Fenton process. The greater performance of the electro-assisted process is justified by the faster regeneration of Fe2+ from the electrochemical reduction and the oxidation contribution of the heterogeneous hydroxyl radical electrogenerated on the dimensional stable anode surface. On the other hand, similar DOC abatements of ca. 60% were attained after 2 h of treatment for all the technologies, being slightly superior for the photo-Fenton process due to the photodecarboxylation of carboxylate-iron complexes. The evaluation of the BOD5 and COD allowed considering the effluent biodegradability enhancement after Fenton's technologies treatment, being feasible their application prior to a biological treatment. From the by-products identification, degradative pathways of the main nitramine pollutants contained in the actual effluent have been proposed. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.