Gradient-Driven Galvanic Effect Enables Self-Sustained Peroxymonosulfate Activation in a Stacked Flow Reactor

Efficient elimination of emerging contaminants (ECs) from complex water matrices remains a challenge for peroxymonosulfate (PMS)-based advanced oxidation processes, which typically require high PMS dosages and suffer from poor oxidant utilization. Here, we report a Fenton-like flow reactor (FFR) composed of stacked layers of immobilized catalysts (Co-carbon nanotube/carbon fiber, Co-CNT/CF). Unlike conventional PMS-activating batch reactors, the FFR harnesses in situ-generated concentration and potential gradients to induce a spontaneous galvanic effect (GE). This macroscale GE enables self-sustained PMS activation, dissolved oxygen reduction, and radical generation without external energy input, thereby overcoming mass transfer limitations inherent to batch reactors. Additionally, it endows the FFR with exceptional adaptability under a wide range of EC concentration, salinity, natural organic matter (NOM), and pH. Notably, increasing wastewater conductivity boosted the treatment capacity by several times, achieving the removal of nearly 100% ECs at a flux rate >1000 mL min^-1. Furthermore, the enhanced microcosmic charge transfer at the catalyst/wastewater interface enabled extremely low PMS usage (≤0.08 mM) and high utilization efficiency (77.5-96.3%). This work introduces a gradient-driven, galvanic-enabled PMS activation pathway that establishes a new design paradigm for cost-effective and energy-saving continuous-flow water purification technologies.