Achieving Polymerization-Oriented Phenolic Pollutant Capture and Minimized Metal Residue in the Permanganate/Polyferric Sulfate Process via a Synergistic Polymerization-Coagulation Strategy.

Permanganate (KMnO4) is widely recognized as a green and efficient oxidant for water purification. During the oxidation of phenolic contaminants, however, soluble coupling products and Mn-containing species (e.g., MnOx colloids and dissolved Mn ions) may remain in the aqueous phase, increasing the burden of downstream separation. Herein, we demonstrate that commercial polyferric sulfate (PFS) can simultaneously serve as a KMnO4 activator and an in situ coagulant, establishing a one-step synergistic polymerization-coagulation strategy for efficient 4-chlorophenol (4-CP) removal with minimal soluble oligomers and leachable metal species. Mechanistic studies reveal that PFS forms a positively charged Fe-(hydr)oxide interface that facilitates KMnO4 activation via electrostatic interactions. Meanwhile, PFS serves as a solid scaffold that stabilizes the critical 4-chlorophenoxyl radical intermediate via bis(4-chlorocatecholato)iron(III) complex formation, thereby driving polymer chain growth. Leveraging its inherent coagulation property, PFS effectively captures organic polymers, increasing chemical oxygen demand (COD) removal from 35.4% to 56.2% within 10 min, while efficiently sequestering MnOx colloids and reducing residual Fe and Mn concentrations in the treated supernatant by 99.2% and 99.4%, respectively. This work addresses limitations of conventional KMnO4 oxidation through in situ polymerization-coagulation, offering a strategy for phenolic pollutant remediation with reduced soluble oligomer accumulation and metal residuals.