Written by My Ph.D. dissertation project focuses on removing contamination using a flow-through electrochemical reactor. addddd
The electrochemistry-based and sorption-based technology was designed to address the challenges posed by mixtures of legacy explosives and IHEs. One challenge from IHEs is competitive kinetics or lack of reactivity altogether due to their different physicochemical properties and reactivates compared to legacy explosives. This technology creates reaction conditions featuring electrochemically-derived non-specific reductants (direct electron transfer and atomic hydrogen, Hads) and oxidants (reactive oxygen species, ROS) capable of degrading all MC indiscriminately. Material and operating conditions were optimized to ensure effluent explosive concentrations meet regulatory requirements. A second challenge is the lack of mechanistic information and product identification of MCs in electrochemical systems. This work then characterized degradation intermediates and products and detail degradation pathways. Third, this technology supports the challenge of ensuring cost-effective management by operation with low power consumption, generation of its own reactive species in situ with little chemical dosing, internal cleanup of residual reactive species prior to discharge, and virtually low cost of material disposal. Finally, the technology addresses the need for the deployment of modular units flexible to wastewater sources. When fully realized, this technology can be adapted to diverse waste configuration demands, including in-line placement within a treatment train or a recirculating batch reactor for a self-contained waste volume
To meet these needs, a two-reactor system containing a flow-through electrochemical reactor that generates reductants based on reactive electrode surfaces and electrolysis of water, and a flow-through GAC column containing a nanosized manganese dioxide (MnO2) catalyst for conversion of injected hydrogen peroxide to hydroxyl radicals. The reactor unit uses low power, features inexpensive stainless steel electrodes, and is capable of sustained, long-term operation without electrode degradation. The overall objective of this work is to optimize the electrochemical and sorption-oxidation flow-through cells for the indiscriminant degradation of munitions with diverse physicochemical properties within manufacturing wastewater.
The central hypothesis for the proposed work is that reaction mechanisms produce favorable conditions for munitions degradation, ring cleavage, and mineralization. Cathodically-induced reactions should promote conditions for reduction and alkaline hydrolysis transformation processes, and rates of these processes should depend on cathode material. A Fenton-like reaction is expected to be supported on the surface-modified GAC in which hydrogen peroxide is converted to hydroxyl radicals through heterogeneous catalytic activation. The coupled reduction, hydrolysis, and oxidation mechanisms are expected to be harnessed to mineralize both organic legacy munitions constituents and new insensitive high explosives.
Laboratory experiments were performed to optimize electrode materials and operating conditions for several MCs and water chemistry conditions. The main research objectives of this study are:
Objective 1. To maximize the impact of the first reduction/hydrolysis step via cathodically-induced reactions on RDX (as a model compound) in synthetic wastewater.
Objective 2. To optimize the performance of the second oxidation step via innovative electro-Fenton-like reactions.
Objective 3. To evaluate the reaction kinetics and transformation pathways of legacy MCs and IHEs in synthetic wastewater within the optimized two-step sequential treatment reactor.
Objective 4. To evaluate the performance of the two-step sequential treatment reactor for contaminant mixtures in a variety of water chemistries.
Nazli Rafei Dehkordi 