975 resultados para peroxide bleaching


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The diffraction pattern of Fe3O4 (not shown) confirmed the presence of only one phase, corresponding to magnetite with a lattice parameter a = 8.357 Å and a crystallite size of 16.6 ± 0.2 nm. The diffraction pattern of MGNC (not shown) confirmed the presence of a graphitic phase, in addition to the metal phase, suggesting that Fe3O4 nanoparticles were successfully encapsulated within a graphitic structure during the synthesis of MGNC. The core-shell structure of MGNC is unequivocally demonstrated in the TEM micrograph shown in Fig. 1b. Characterization of the MGNC textural and surface chemical properties revealed: (i) stability up to 400 oC under oxidizing atmosphere; (ii) 27.3 wt.% of ashes (corresponding to the mass fraction of Fe3O4); (iii) a micro-mesoporous structure with a fairly well developed specific surface area (SBET = 330 m2 g-1); and (iv) neutral character (pHPZC = 7.1). In addition, the magnetic nature of MGNC (Fig. 2) is an additional advantage for possible implementation of in situ magnetic separation systems for catalyst recovery.

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In this work, a wheat and hemp lignin (Sarkanda, Granit S.A.) has been used as raw material for the development of metal-free activated carbons. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of 4-nitrophenol (4-NP; 5 g L-1) during 24 h experiments conducted at relatively mild operating conditions (p = 1 atm, t = 50 °C, pH = 3, catalyst load = 2.5 g L-1 and [H2O2]0 = 17.8 g L-1). First, the lignin was carbonized under N2 atmosphere followed by the activation of the obtained non-porous carbon (LG) under air atmosphere at different temperatures (150 to 350 ºC), leading to the generation of significant porosity.

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Hybrid magnetic carbon composites have been recently proposed as the next step in the evolution of catalysts for catalytic wet peroxide oxidation (CWPO), with several synergistic effects arising from the combination of the high catalytic activity of metal species with the proven catalytic properties of carbon-based materials in CWPO [1]. Bearing this in mind, this work sought the development of novel magnetic carbon xerogels, composed by interconnected carbon microspheres with iron (Fe) and/or cobalt (Co) microparticles embedded in their structure. As inferred from the extensive characterization performed, materials with distinctive properties were obtained upon inclusion of different metal precursors during the sol-gel polymerization of resorcinol and formaldehyde, followed by thermal annealing.

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Grant no. R-803525-04.

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Mode of access: Internet.

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Spine title: Dyeing & bleaching.

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Jacob van Ruisdael; 1 ft. 4 59/64 in.x 1 ft. 2 61/64 in.; oil on canvas

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A carrier distillation spectrochemical method has been successfully adapted to direct reading spectrometry. Direct reading techniques have been developed for the rapid analyses of aluminum in plutonium peroxide to demonstrate the capability of direct reading for process impurity control.

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Printed in Great Britain.

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"Portions of this book first published [by the Dept. of Marine Engineering, U. S. Naval Academy] as a part of Combustion engines manual and...of Internal combustion engines."

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Mode of access: Internet.