Date of Award

Fall 1-1-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical and Environmental Engineering (ENAS)

First Advisor

Kim, Jae-Hong

Abstract

Catalytic water treatment technologies hold great promise for degrading even the most recalcitrant contaminants of emerging concern (CECs). Heterogeneous catalytic processes are especially appealing, providing the benefits of easy catalyst recovery and reduced risk of secondary pollution. However, heterogeneous reactions often suffer from mass transfer limitations, and the development of catalyst materials that are sufficiently active, selective, and stable under the conditions necessary for pollutant degradation remains challenging. Furthermore, synthesis of catalyst materials, particularly those with desirable catalytic properties and novel architectures, are often time- and energy-intensive and involve expensive materials and/or equipment. In this work, we address these challenges by developing electrochemical approaches to synthesize and regenerate state-of-the-art catalyst materials and enhance the performance and sustainability of catalytic water treatment processes. First, we present a novel synthesis route to produce single-atom catalysts (SAC) supported on oxidized, commercially available carbon electrodes. In contrast to typical SAC synthesis methods, our approach, based on the phenomenon of underpotential deposition (UPD), can be performed at ambient temperature and pressure, and on the scale of minutes. We then demonstrate the strong catalytic performance of our UPD-synthesized SACs by applying a Co SAC for selective electrocatalytic nitrate reduction to ammonia, a promising reaction for simultaneous water remediation and fertilizer production. Second, we adapt our UPD method to achieve facile and cost-effective synthesis of a free-standing catalytic Co SAC membrane, consisting of Co active sites dispersed on an oxidized carbon paper support. The SAC membrane demonstrates excellent single-pass performance for peroxymonosulfate (PMS) activation, an advanced oxidation process (AOP) for degrading organic contaminants. In addition, we show that periodic regeneration of the membrane via UPD can fully recover its catalytic performance, enabling long-term operation by reversing the effects of catalyst deactivation under the harsh conditions of PMS activation. Lastly, we develop a flowthrough electrochemical system to enhance oxidative organic pollutant degradation using hydrogen peroxide and naturally present iron as a decentralized catalyst supply. Although the initial addition of hydrogen peroxide to iron-containing groundwater can result in degradation of organic pollutants via homogeneous Fenton oxidation, the effectiveness of this process is severely hindered by the circumneutral pH of typical groundwater and limited concentrations of iron catalyst. We demonstrate that by passing this reacted solution through an electrochemical flow cell, we can greatly enhance iron utilization and pollutant degradation via anodic redissolution and cathodic regeneration of iron. Paired with emerging technology for electrochemical hydrogen peroxide production from oxygen gas, this electrochemically enhanced Fenton process presents an opportunity for "reagent-free" groundwater treatment, in which organic pollutants are degraded using air and electricity as the only inputs.

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