Green Decomposition of Organic Dyes Using Octahedral Molecular Sieve Manganese Oxide Catalysts

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Author list: Sriskandakumar T, Opembe N, Chen CH, Morey A, King'ondu C, Suib SL

Publisher: American Chemical Society

Place: WASHINGTON

Publication year: 2009

Journal: The Journal of Physical Chemistry A (1089-5639)

Journal acronym: J PHYS CHEM A

Volume number: 113

Issue number: 8

Start page: 1523

End page: 1530

Number of pages: 8

ISSN: 1089-5639

eISSN: 1520-5215

Languages: English-Great Britain (EN-GB)

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Abstract

The catalytic degradation of organic dye (methylene blue, MB) has been studied using green oxidation methods (tertiary-butyl hydrogen peroxide, TBHP, as the oxidant with several doped mixed-valent and regular manganese oxide catalysts in water) at room and higher temperatures. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The most active catalysts were those of Mo6+- and V5+-doped OMS. Rates of reaction were found to be first-order with respect to the dye. TBHP has been found to enhance the MB decomposition, whereas H2O2 does not. Reactions were studied at pH 3-11. The optimum pH for these reactions was pH 3. Dye-decomposing activity was proportional to the amount of catalyst used, and a significant increase in catalytic activity was observed with increasing temperature. X-ray diffraction (XRD), energy dispersive spectroscopy (EDX), and thermogravimetric analysis (TGA) studies showed that no changes in the catalyst structure occurred after the dye-degradation reaction. The products as analyzed by electrospray ionization mass spectrometry (ESI-MS) showed that MB was successively decomposed through different intermediate species.

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