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

•The •OH radicals in Fenton and UV/Fenton processes were analyzed quantitatively.•The substitutions affected the catalytic activity of magnetite in •OH generation.•Cr substituted magnetite displayed the best catalytic activity in •OH generation.•The relationship between •OH generation and pollutant degradation was discussed.•Multivariate analyses were carried out to interpret the main influence factors.

In this paper, the heterogeneous Fenton and UV/Fenton catalytic activities of transition metal substituted magnetites, Fe3−xMxO4 (M = Ti, Cr, Mn, Co and Ni), were compared in the perspective of •OH radicals generation. In heterogeneous Fenton reaction, the substitutions of Cr(III), Mn(II) and Co(II) enhanced the rate of •OH formation, while Ni(II) and Ti(VI) showed the negative effect. In heterogeneous UV/Fenton reaction, the Ni(II) and Co(II) introduction did not show notable changes on •OH generation efficiency, whetreas the Cr(III), Ti(VI) and Mn(II) incorporation improved this reaction and accordingly enhanced the UV/Fenton catalytic activity of magnetite. Redundancy and Pearson correlation analyses were carried out to interpret the influence factors in Fenton and UV/Fenton reactions.

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