title: Green decomposition of organic dyes using octahedral molecular sieve manganese oxide catalysts.
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 Mo(6+)- and V(5+)-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 H(2)O(2) 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.
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs 06269-3060, USA.
authors.forename: Thamayanthy
authors.initials: T
authors.lastname: Sriskandakumar
authors.forename: Naftali
authors.initials: N
authors.lastname: Opembe
authors.forename: Chun-Hu
authors.initials: CH
authors.lastname: Chen
authors.forename: Aimee
authors.initials: A
authors.lastname: Morey
authors.forename: Cecil
authors.initials: C
authors.lastname: King'ondu
authors.forename: Steven L
authors.initials: SL
authors.lastname: Suib
mesh_terms: D002384:Catalysis; D004396:Coloring Agents / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry*; D008751:Methylene Blue / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013052:Spectrometry, X-Ray Emission; D013696:Temperature; D013818:Thermogravimetry; D014639:Vanadium / Q000737:chemistry; D014867:Water; D014961:X-Ray Diffraction; D020122:tert-Butylhydroperoxide / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D017895:Manganese Compounds; D016877:Oxidants; D010087:Oxides; D014639:Vanadium; D014867:Water; C027424:manganese oxide; D008982:Molybdenum; D020122:tert-Butylhydroperoxide; D006861:Hydrogen Peroxide; D008751:Methylene Blue