Novel active heterogeneous Fenton system based on Fe3−xMxO4 (Fe, Co, Mn, Ni): The role of M2+ species on the reactivity towards H2O2 reactions

The distinct effects of Mn substitution on the reactivity of magnetite in heterogeneous Fenton reaction and Pb(II) adsorption

“…Sample FM1 with lower Mn content displayed the strongest activity, while for other samples, the activity did not vary obviously with the increase in Mn content. From previous studies [12,13], the strong Fenton activity of magnetite originates from the active species Fe 2+ on magnetite surface and the fast electron transfer between octahedral Fe 2+ and Fe 3+ . The substitution of transition metals, e.g., Cr 3+ [55] and V 3+ [18], improved the Fenton activity of magnetite.…”

“…The octahedral Mn 2+ and Mn 3+ accelerate the electron transfer to regenerate the Fenton active species Fe 2+ , which leads to the strong Fenton activity of FM1 (Fig. A.1) [13,23]. Moreover, the catalytic performance of magnetites with lower Mn substitution than FM1 (Table A.1) was tested in the AOII degradation.…”

“…Fe 2+ plays an important role as an electron donor to initiate the AOPs [12]. The accommodation of Fe 2+ and Fe 3+ on the octahedral sites allows the Fe species to be reversibly oxidized and reduced while keeping the structure unchanged [13]. In most natural magnetites, iron cations are isomorphously substituted by divalent (Co, Ni, Mn, etc.…”

“…in catalyzing the heterogeneous Fenton reaction, ascribed to the presence of highly active Fe 2+ species on magnetite surface and the fast electron transfer between Fe 2+ and Fe 3+ on the octahedral sites [13,18]. The incorporation of transition metals in magnetite obviously affects the Fenton reactivity of magnetite.…”

“…The incorporation of transition metals in magnetite obviously affects the Fenton reactivity of magnetite. The introduction of Co [13], Ti [19,20], V [18] and Cr [21] improves the Fenton catalytic activity of magnetite, while Ni shows an inhibitory effect [13]. Such distinct effects greatly depend on the oxidation states and occupancy of substituting cations [22,23].…”