Synergetic Relay of Phenoxyl-Radical-Mediated Oligomerization and Aromatic-Ring-Opening Processes for Organic Wastewater Treatment

Abstract

Efficient removal of recalcitrant aromatic compounds in organic wastewater is hindered by ambiguous reaction pathways in conventional single-process polymerization or ring-opening mineralization. Herein, we report a synergistic relay strategy that integrates phenoxyl-radical-mediated oligomerization and aromatic-ring-opening pathways for the highly efficient treatment of organic wastewater. This approach couples an initial high-valence iron-oxo species (HVIO)-driven oligomerization via formal hydrogen atom transfer at one site with a subsequent singlet oxygen (¹O₂)-mediated ring-opening reaction at an adjacent site, enabled by a dual-single-atom Fe₁Cu₁/TiO₂ photocatalyst. Under solar-light irradiation, photoinduced electrons are transferred to peroxymonosulfate (PMS) at the Fe₁ site, which acts as a critical activator to generate HVIO for oligomerization-based removal. Simultaneously, holes oxidize PMS at the Cu₁ site to produce ¹O₂, leading to efficient aromatic-ring-opening. This sequential strategy achieved nearly 72% chemical oxygen demand removal with 23% carbon recovery into separable polymer products within 10 min for the phenol and ultimately reached complete removal with a rate constant of 1.21 min⁻¹, significantly surpassing most reported values. Moreover, the system exhibited excellent stability and long-term activity in a custom-designed photo-filter reactor, highlighting its practical potential. By coupling oligomerization and mineralization, this work provides a groundbreaking and versatile platform for treating complex organic wastewater.