Electrochemically-Induced in situ Degradation of Legacy Munitions and Insensitive High Explosives in Manufacturing Wastewater

Dr. Philip Larese-Casanova | Northeastern University

ER19-1130

Objective

The presence of new insensitive high explosives (IHE) co-mingled with legacy munitions constituents (MC) has posed new challenges to treating explosives manufacturing waste streams and has prompted a demand for innovative treatment strategies. To meet the need for improved, cost-effective water treatment technologies for MCs, the investigators have developed a flow-through electrochemical reactor that generates reductants and reactive oxygen species in situ based on reactive electrode surfaces and electrolysis of water. The reactor unit uses low power and is capable of sustained, long-term operation without chemical additives. The objective of this project is to adapt the current electrochemical design for the indiscriminant degradation of MCs with diverse physicochemical properties within manufacturing wastewater.

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Technical Approach

The central hypothesis of this project is that coupled reaction mechanisms produce favorable conditions for MC degradation, ring cleavage, and mineralization. A single chamber flow-through electrochemical reactor is envisioned wherein three modes of contaminant degradation are possible:

  1. the direct reduction of MCs by electron transfer or adsorbed atomic hydrogen at cathode surfaces,
  2. alkaline hydrolysis within a downstream zone of high pH, and
  3. oxidation by in situ generated reactive oxygen species (ROS) such as hydroxyl radicals via electro-Fenton-like reaction.

Laboratory experiments with bench-scale reactors will be conducted to optimize the electrode materials and operating conditions to achieve near complete mineralization of the targeted MCs to form low molecular weight carbon and nitrogen compounds. Kinetic studies and degradation pathway identification will help identify reaction mechanisms occurring in solution and at electrode surfaces for each of the legacy MCs and IHEs. Experiments will also evaluate the influence of co-mingled MCs, other dissolved contaminants and solutes, and real wastewater chemistry.

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Benefits

This project will support the treatment strategies for liquid wastes containing multiple MCs from diverse source streams. If successful, the technological development will result in an electrochemical reactor that delivers a sustained in situ generation of several reductants and ROS for the rapid and complete degradation of legacy MCs and IHE. The technology will generate nonspecific reductants and oxidants applicable to a variety of contaminants in mixture simultaneously without the need for chemical reagent addition. Changes in solution pH, redox conditions, and reactants are self-contained within the reactor which precludes the need for effluent chemical adjustment prior to discharge or further treatment. Reaction conditions will be created using inert and cost-effective materials (stainless steel, graphite, activated carbon) under low electric power. When the technology is fully realized, managers will be able to deploy modular reactor units adaptable to a variety of waste sources, chemistries, and flow conditions. The project will also serve the scientific community by providing insight to MC transformation mechanisms by ROS, sorbed atomic hydrogen, and modified electrode surfaces. 

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Points of Contact

Principal Investigator

Dr. Philip Larese-Casanova

Northeastern University

Phone: 774-307-0392

Program Manager

Environmental Restoration

SERDP and ESTCP

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