Revisiting the design of direct-electron-transfer oxidation systems: Synergistic roles of thermodynamic and hydrodynamic properties

Direct electron transfer (DET)-mediated peroxide-based advanced oxidation processes have emerged as competitive technologies for treating recalcitrant emerging micropollutants. Current research on these technologies predominantly concentrates on catalyst modifications to enhance water purification. However, a comprehensive approach integrating thermodynamic and hydrodynamic optimizations remains underexplored. This work uncovers their critical role in activating the peroxide of peracetic acid (PAA) via a cobalt nanoparticle-functionalized carbon nanotube (Co-CNT) membrane in a single-pass filtration. Notably, this system achieves over 50 % higher 4-chlorophenol removal than the pristine CNT membrane/PAA system, with a 145-fold kinetics acceleration compared to batch processes and complete removal within 4.3 s. Co nanoparticles augment PAA interaction via high charge accumulation. This enhancement thermodynamically boosts the overall oxidative potential of such a DET-mediated system, facilitating electron abstraction from micropollutants. Additionally, computational fluid dynamics demonstrates that the advection and spatial confinement by the filtration compress the diffusion boundary layer by 2 orders of magnitude versus the batch counterpart, and thus shorten the diffusion timescale below the advection timescale. This hydrodynamic variation achieves advection-enhanced mass transport and increases the frequency of interactions between reactants with the DET-mediated catalyst surface. Overall, this study revisits the design of DET-mediated peroxide-based systems, underscoring the necessity of concurrent thermodynamics and hydrodynamic optimization in boosting catalytic efficiency for water purification.