In-situ generation of multi-homogeneous/heterogeneous Fe-based Fenton catalysts toward rapid degradation of organic pollutants at near neutral pH.

In this study, an in-situ generated multi-homogeneous/heterogeneous Fe-based catalytic system was developed, which exhibited a high efficiency for the production of •OH and rapid degradation of various organic pollutants in a near neutral pH range (5–8). The mechanism for the rapid decomposition of H2O2 and the generation of •OH were investigated in detail. The results indicated that, besides the introduced Fe2+, the in-situ generated various iron species including Fe(OH)+, Fe(OH)2, Fe3+, ferrihydrite (Fh), γ-FeOOH and α-FeOOH as well as FeII/Fh, FeII/γ-FeOOH and FeII/α-FeOOH could simultaneously act as homogeneous and heterogeneous Fenton reaction catalysts. The dropwise addition manner of Fe2+ greatly improved the catalytic efficiency of Fe2+ ions in near neutral pH environment, while the in-situ generated nanosized Fh, γ-FeOOH and α-FeOOH could supply numerous active catalytic sites. After degradation, the ferrous ions could be transformed to various crystalline iron oxides by the catalytic phase transformation. This study presents a method towards the rational design of novel Fenton catalysts for wastewater treatment.