Synergistic regulation of iron cycle and hydroxyl radical generation in sodium percarbonate-based Fenton reaction enables efficient degradation of chlorinated hydrocarbons.

Iron-catalyzed Fenton-like systems driven by sodium percarbonate (SPC) hold great potential for the oxidative degradation of organic pollutants, but the sluggish Fe(Ⅲ)/Fe(Ⅱ) redox cycle and deficient electron replenishment limit the rapid generation of reactive oxygen species (ROS). Herein, we report a bifunctional cocatalyst derived from polydopamine (PDA) that simultaneously accelerates the Fe(Ⅲ)/Fe(Ⅱ) cycle and promotes the generation of hydroxyl radicals in the Fe(Ⅲ)/SPC system. The chelation of phenolic hydroxyl groups with iron ions initiates ligand-to-metal charge transfer, enabling the direct reduction of Fe(Ⅲ) to Fe(Ⅱ). Concurrently, the catechol groups elongate the Fe-O bond of FeOH2 +, elevating the oxidation potential of Fe(Ⅲ) and lowering the energy barrier for H2O2-mediated Fe(Ⅲ) reduction, further promoting Fe(Ⅱ) regeneration. The Fe(Ⅲ)/SPC/PDA system exhibits self-acidification capability, enabling efficient degradation of chlorinated hydrocarbons over a wide pH range and in complex real-world water matrices. Under optimal conditions of 2.5 mM Fe(III), 2 mM SPC, and 200 mg/L PDA, trichloroethylene can be completely removed within 30 min, achieving a removal rate as high as 0.209 min-1. The PDA cocatalyst also demonstrates excellent recyclability, outperforming most previously reported cocatalysts. The potent regulatory effect of PDA is extended to other iron/SPC-based advanced oxidation processes and the removal of various recalcitrant pollutants. This study presents an environmentally friendly cocatalyst that effectively enhances the sustained activity of Fenton-like oxidation systems in water decontamination.