Interfacial Redox Regulation of γ-Al2O3-Supported MnFe2O4 for Oxidative Chain Scission in Concentrated Poly(vinyl alcohol) Gel-Forming Networks.

Abstract

Concentrated poly(vinyl alcohol) (PVA) gel-forming networks are characterized by extensive hydrogen bonding, pronounced chain entanglement, and restricted molecular diffusion, which collectively limit oxidant accessibility and impede efficient oxidative transformation. Herein, a γ-Al₂O₃-supported MnFe₂O₄ catalyst (FMA) was developed to regulate interfacial redox properties and enhance H₂O₂ activation, thereby promoting oxidative chain scission of concentrated PVA gel-forming networks. The γ-Al₂O₃ support effectively suppressed MnFe₂O₄ aggregation, leading to enhanced specific surface area and increased exposure of accessible Fe/Mn active sites. Under optimized conditions, the FMA/H₂O₂ system achieved approximately 90% PVA conversion within 120 min, together with 89.2% TOC removal and a decrease in molecular weight from 68,892 to 2063 Da, demonstrating efficient oxidative chain scission and deep mineralization. Mechanistic investigations using XPS, EPR, and radical-quenching experiments revealed that synergistic Fe/Mn redox cycling promoted H₂O₂ activation and hydroxyl radical generation, which dominated PVA chain cleavage. The catalyst exhibited excellent stability with limited metal leaching during repeated cycles. This work demonstrates that γ-Al₂O₃-mediated interfacial regulation provides an effective strategy for designing supported metal oxide catalysts toward controlled transformation of highly entangled gel-related polymer networks, providing insights into the oxidative deconstruction of PVA-based gel and hydrogel systems.