Electrochemical treatment of recalcitrant organic contaminants utilizing activated carbon-based heterogeneous catalysts

The growing ubiquity of recalcitrant organic contaminants, or persistent organic pollutants (POPs), in the aqueous environment poses risks to effective and efficient water treatment and reuse. These types of pollutants are not sufficiently naturally degraded or removed by conventional treatment, are typically environmentally mobile, and can have negative ecotoxicological effects. Emerging treatment methods for the removal of POPs in aqueous waste streams seek to overcome limitations with conventional treatment with designs that are cost-effective, robust, and sustainable. Electrochemical advanced oxidation processes (EAOPs) are a promising form of treatment technology using electricity and efficient electrode materials aimed at generating highly oxidative radicals for the degradation of POPs. Concurrently, activated carbons (AC) are effective adsorbents and have properties that make them robust materials for implementation in many treatment technologies. In this research, EAOP technologies and AC-based heterogeneous catalysts are combined to treat aqueous waste streams laden with POPs effectively and efficiently. AC is a viable material for the heterogeneous catalysis of hydrogen peroxide (H2O2) to form oxidative hydroxyl radicals and can be further modified with nanomaterials like manganese oxide nanopowder for the highly effective formation of radicals. This AC-based heterogeneous catalyst was combined with a flow-through electrochemical reactor generating H2O2 in-situ upon a hydrophobic carbonaceous cathode for the combined degradation and removal of the legacy munitions' constituent RDX. Insights gained from this research was then utilized to design a novel three-dimensional electrochemical flow-through reactor employing AC encased in a stainless-steel mesh as a cathode for the effective removal and degradation of a model recalcitrant contaminant p-nitrophenol (PNP). The innovative design was additionally utilized for the electrochemical regeneration of AC sufficiently saturated with PNP. The research and design objectives are focused on determining the optimal materials, design, and operational parameters of EAOPs and AC-based heterogeneous catalysts for the effective treatment of these model pollutants. A focus was placed on cost-effective and sustainable solutions to enhance the applicability of these technologies for more large-scale, ubiquitous treatment of both source and non-source pollutant waste streams. It is anticipated these insights hold great promise to eliminate analogous contaminants as well as mixtures.--Author's abstract