Bletsa E, Zaccone C, Miano T, Terzano R, Deligiannakis Y. Natural Mn-todorokite as an efficient and green azo dye-degradation catalyst.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020;
27:9835-9842. [PMID:
31925697 DOI:
10.1007/s11356-019-07524-6]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Accepted: 12/25/2019] [Indexed: 06/10/2023]
Abstract
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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