Remarkable effect of Co and Mn on the activity of Fe3−M O4 promoted oxidation of organic contaminants in aqueous medium with H2O2

The valence and site occupancy of substituting metals in magnetite spinel structure Fe3−xMxO4 (M = Cr, Mn, Co and Ni) and their influence on thermal stability: An XANES and TG-DSC investigation

“…For instance, metal substitution (e.g., Cr, Co, Mn, Ni) in magnetite produces systematic variation in magnetic properties, e.g., saturation magnetization, the Curie temperature change, coercivity and electrical resistivity changes [9]. The introduction of Co 2þ , Mn 2þ , V 3þ and Ti 4þ in the spinel structure remarkably increases the catalytic activity of magnetite [10e12] whereas Ni 2þ shows an inhibitory effect [10]. Co 2þ improves the catalytic activity of magnetite by initiating H 2 O 2 decomposition to produce OH (Eq.…”

The constraints of transition metal substitutions (Ti, Cr, Mn, Co and Ni) in magnetite on its catalytic activity in heterogeneous Fenton and UV/Fenton reaction: From the perspective of hydroxyl radical generation

“…As indicated by previous researches [10,11,[19][20][21], some substitutions obviously varied the catalytic activity of magnetite in heterogeneous Fenton reaction. The introduction of Mn 2+ [10,11], Co 2+ [10,11], V 3+ [22], Ti 4+ [21] and Cr 3+ [12,19] improved the catalytic activity of magnetite in the degradation of organic pollutants (e.g., methylene blue, phenol and acid orange II), while Ni 2+ showed an inhibitory effect [11]. These variations relied on two aspects, i.e., the generation rate of • OH radicals and adsorption ability of organic pollutants and H 2 O 2 onto magnetite surface.…”

“…2). [10][11][12]19], the presence of Co, Mn and Cr in magnetite structure engendered a remarkable increase of Fenton reactivity of magnetite towards the degradation of methylene blue. In this study, these substitutions obviously improved the activity of magnetite in • OH generation, which can well explain their positive effect on the Fenton activity of magnetite.…”

“…(1)) to form highly reactive and non-selective hydroxyl radicals ( • OH). With a quite high redox potential (2.80 eV), • OH radicals can oxidize and mineralize most organic substances in environment [10][11][12]. Previous studies have shown that • OH production is a critical factor affecting the degradation efficiency of contaminants in various water treatment techniques [1,[13][14][15][16].…”

The contribution of vanadium and titanium on improving methylene blue decolorization through heterogeneous UV-Fenton reaction catalyzed by their co-doped magnetite

“…Especially in environmental engineering, the incorporation of transition metals into magnetite, such as Mn, Cr and Co, can greatly increase the heterogeneous Fenton catalytic activity of magnetite with high efficiency and easy recycle in wastewater purification, e.g. printing and dyeing water [4,5] and wastewater containing persistent organics [6]. Metalsubstituted magnetites have been considered as an outstanding candidate of catalysts in advanced oxidation processes (AOPs).…”