Enhanced Fenton Catalytic Efficiency of γ‑Cu–Al₂O₃ by σ‑Cu²⁺–Ligand Complexes from Aromatic Pollutant Degradation

Abstract

Mesoporous Cu-doped γ-Al₂O₃ (γ-Cu–Al₂O₃) was prepared via an evaporation-induced self-assembly process, in which Cu^+/2+ was co-incorporated into mesoporous γ-Al₂O₃ by chemical bonding of Al–O–Cu. The catalyst was found to be highly effective and stable for the degradation and mineralization of aromatic pollutants, as demonstrated with bisphenol A, 2,4-dichlorophenoxyacetic acid, ibuprofen, diphenhydramine, and phenytoin in the presence of H₂O₂ under neutral pH conditions. In addition, the high utilization efficiency of H₂O₂ was maintained at approximately 90% prior to the disappearance of the initial aromatic pollutants. On the basis of all of the characterization results, the pollutant degradation processes predominantly occurred on the surface of the catalyst due to the formation of σ-Cu–ligand complexes between the phenolic OH group and the surface Cu. In the reaction system, in addition to the unselective oxidation by ^•OH, H₂O₂ directly attacked the σ-Cu²⁺-complexes aromatic ring with the phenolic OH group, which resulted in the formation of ^•OH and HO-adduct radicals that were oxidized to hydroxylation products by reduction of Cu²⁺ in the σ-Cu²⁺-complexes to Cu⁺. The process prevented Cu²⁺ from oxidizing H₂O₂ to form HO₂^•/O₂^•– or O₂, and enhanced the Cu⁺/Cu²⁺ cycle, the formation of ^•OH, and the utilization efficiency of H₂O₂. Therefore, an extraordinarily high degradation and mineralization of the aromatic pollutants was observed