Sustainable mineralization of bisphenol A via iron-oxide-fortified manganese catalysts: Integrating radical and nonradical pathways for advanced wastewater treatment

Abstract

Nanoparticulate manganese dioxide (MnO2) was integrated into a ferric oxide (Fe2O3) framework via a coprecipitation technique followed by thermal annealing, yielding a porous composite structure enriched with surface pores and microcracks. The Mn:Fe stoichiometry played a critical role in determining the crystalline architecture, catalytic performance, and stability of the composites. In dark conditions, the degradation of Bisphenol A (BPA) through peroxydisulfate (PDS)-mediated electron transfer did not achieve complete mineralization. Under UV irradiation, however, the composite facilitated near-complete BPA mineralization due to a synergistic interaction between radical generation and electron transfer processes. Notably, nonradical mechanisms predominantly governed BPA degradation, with the PDS-MnO2 interaction being central to its efficiency. The Fe2O3 matrix improved structural stability, significantly reducing manganese ion leaching. Specifically, MnFe-12 (Mn:Fe 1:2) exhibited a 2200-fold reduction in Mn dissolution compared to bare MnO2. In situ X-ray absorption spectroscopy revealed that radical-mediated processes elevated the oxidation state of Mn ions, while Fe ions remained unchanged. The study highlights the importance of integrating radical and nonradical pathways to achieve efficient and sustainable degradation of persistent pollutants, offering insights for the rational design of advanced oxidation systems with enhanced structural integrity and catalytic efficiency.