High-salinity composite organic wastewater electrochemical treatment: A Janus system coupling high-valent iron oxidation with atomic hydrogen-mediated reductive detoxification.

The advanced treatment of high-salinity composite organic wastewater is fundamentally constrained by a critical trade-off between efficient refractory pollutant mineralization and the deleterious accumulation of toxic chlorinated byproducts. In this study, we report a Janus electrochemical treatment system that transcends these limitations by synergistically coupling selective high-valent iron (FeIV) oxidation with atomic hydrogen (H*)-mediated reductive detoxification using highly dispersed manganese species anchored on N,P-codoped carbon (Mn-NP/C). Electronic structure modulation via P-incorporation induces localized charge redistribution to create electron-rich Mn centers, significantly lowering the energy barrier for in-situ H* generation. Mechanistic investigations reveal that cathodic H* drives a multi-functional reductive pathway that accelerates the iron cycle to sustain a steady-state FeIV concentration 1.7 times higher than that of conventional systems. Simultaneously, H* mediates the exhaustive dechlorination of toxic anodic oxidation intermediates and the reduction of NO3- back into the nitrogen removal cycle, effectively eliminating thermodynamic dead-ends. Consequently, this integrated redox system enhances the removal efficiencies of total organic carbon and total nitrogen by up to 3.4- and 1.6-fold, respectively, while simultaneously reducing total organic chlorine by 97.6%. When applied to actual coal chemical wastewater, the system satisfied strict national discharge standards for both COD and NH3N. Notably, it achieved an operational cost of 1.65 $/kg COD, representing a 1.7- to 27.8-fold reduction compared to reported treatment processes. This work provides a robust and economically compelling strategy for the sustainable decontamination of complex high-salinity industrial wastewater.