Stable Single-Pass Electrochemical Oxidation of Trace 1,4-Dioxane in Groundwater via Multistage Reactors with Current...

Electrochemical oxidation (EO) can destroy a broad range of water contaminants, but single-stage, single-pass reactors often require high energy input and low water flux to achieve meaningful removal, limiting practical deployment. These constraints are acute for 1,4-dioxane, a persistent groundwater contaminant and potential human carcinogen, where long-term operation in low-conductivity water matrices is further hindered by anode degradation, cathodic scaling, and formation of harmful byproducts. Here, we develop and validate a scalable strategy that combines a multistage, flow-through EO reactor with on/off current pulsing using commercially available Ti₄O₇ mesh anodes. In a laboratory electrolyte (50 mM NaClO₄), 1,4-dioxane degradation in a single-stage cell followed pseudo-first-order kinetics (k = 0.103 min^-1), and staging substantially increased single-pass removal across practical fluxes. In synthetic groundwater, pulsed operation markedly suppressed mineral scaling and reduced perchlorate byproduct formation by 44-82% relative to direct-current electrolysis while improving operational stability. Integrating staging with pulsing delivered the most durable performance: a four-stage reactor operated at 15 s on/15 s off maintained stable treatment in groundwater at an environmentally relevant 1,4-dioxane concentration (0.1 mg/L), achieving 60-80% single-pass removal (average ∼70%) over 20 days with minimal voltage rise. These results demonstrate that coupling reactor staging with pulsed electrolysis mitigates key failure modes and byproduct risks, providing a practical design and operating framework for long-lasting EO as point-of-use/point-of-entry treatment of trace contaminants in groundwater.