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Natural Mn-todorokite as an efficient and green azo dye–degradation catalyst


A natural Mn mineral, i.e., todorokite [(Ca,Na,K)X(Mn4+,Mn3+)6O12·3.5H2O], has been collected in the Apulia region, south of Italy, and evaluated as an oxidation catalyst for the degradation of methyl orange (MO) dye. This Mn-todorokite mineral has been firstly characterized by X-ray diffraction, wavelength-dispersive X-ray fluorescence, BET, scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and thermogravimetry. Catalytic dye-degradation data show that this Mn-todorokite can operate under strongly oxidizing potentials (Eh > + 400 mV) vs. standard hydrogen electrode performing fast MO degradation (t1/2 < 1 min). A detailed study using electron paramagnetic resonance spectroscopy revealed that, under oxidative conditions (Eh > + 450 mV), the active Mn centers of todorokite evolve rapidly through Mn3+/Mn4+ states and this is correlated with the fast catalytic degradation of MO. These results suggest Mn-todorokite mineral as an efficient, low-cost, and green catalyst which can be used for industrial and environmental purposes.

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E.B. thanks Dr. George A. Sotiriou, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet (Solna, Sweden), for SSA measurements. C.Z. thanks Dr. Giorgio S. Senesi, CNR-Istituto per la Scienza e la Tecnologia dei Plasmi (Bari, Italy), for SEM analysis.

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Correspondence to Claudio Zaccone.

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Responsible editor: Santiago V. Luis

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Bletsa, E., Zaccone, C., Miano, T. et al. Natural Mn-todorokite as an efficient and green azo dye–degradation catalyst. Environ Sci Pollut Res 27, 9835–9842 (2020).

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