Controlling Fe(IV)O-mediated catalytic polymerization coupled with oligomer management for high-salinity coking wastewater treatment

Polymerization transfer (PT) technology is highly advantageous for treating high-salinity wastewater due to its high tolerance to coexisting anions and superior electron utilization efficiency. Here, we report the unusual simultaneous achievement of rapid pollutant removal (pseudo-first-order rate constant of 0.15 min −1 , 56.0-fold higher than unmodified counterparts) and high PT ratio (>65 %) in a peroxymonosulfate (PMS) activation system. This was achieved by simply tuning the Fe content within a rationally designed Fe/N engineered pine sawdust biochar catalyst. Performance enhancement stems from Fe-induced graphitization improving electron transfer, coupled with N-induced moderate orbital hybridization between Fe 3 d (Fe/N biochar) and O 2 p (PMS) atomic states, optimizing PMS adsorption-desorption and yielding the lowest energy barrier for Fe(IV) O formation. Remarkably, the system maintains robust performance under high salinity conditions (500 mM Cl − , HCO 3 − , NO 3 − , and SO 4 2− ) and achieves 67.5–77.3 % chemical oxygen demand (COD) removal during 17-day continuous-flow treatment of real coking wastewater, where polymerization-mediated organic removal through C C/C O coupling. Furthermore, residual oligomers are efficiently removed by subsequent activated carbon (AC) adsorption or poly-ferric sulfate (PFS) coagulation, establishing an integrated “catalytic polymerization-AC/PFS polishing” paradigm for sustainable treatment of refractory organics in high salinity coking wastewater.