Core-shell nanocomposites prepared by hierarchical co-assembly: the role of the carbon shell in catalytic wet peroxide oxidation processes

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.

Metal-free catalysts derived from lignin for efficient wet peroxide oxidation

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.

Development of magnetic carbon xerogels for catalytic wet peroxide oxidation

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.

Rapid determination of aluminum in plutonium peroxide cake /

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.

Gas turbines and jet propulsion, including rocket, hydrogen peroxide, and nuclear power plants: theory and application.

"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."

Urea formaldehyde foam insulation.

Cover title.

Urea based osmoregulation and endocrine control in elasmobranch fish with special reference to euryhalinity

Since the landmark contributions of Homer Smith and co-workers in the 1930s there has been a considerable advance in our knowledge regarding the osmoregulatory strategy of elasmobranch fish. Smith recognised that urea was retained in the body fluids as part of the 'osmoregulatory ballast' of elasmobranch fish so that body fluid osmolality is raised to a level that is iso- or slightly hyper-osmotic to that of the surrounding medium. From studies at that time he also postulated that many marine dwelling elasmobranchs were not capable of adaptation to dilute environments. However, more recent investigations have demonstrated that, at least in some species, this may not be the case. Gradual acclimation of marine dwelling elasmobranchs to varying environmental salinities under laboratory conditions has demonstrated that these fish do have the capacity to acclimate to changes in salinity through independent regulation of Na+, Cl- and urea levels. This suggests that many of the presumed stenohaline marine elasmobranchs could in fact be described as partially euryhaline. The contributions of Thomas Thorson in the 1970s demonstrated the osmoregulatory strategy of a fully euryhaline elasmobranch, the bull shark, Carcharhinus leucas, and more recent investigations have examined the mechanisms behind this strategy in the euryhaline elasmobranch, Dasyatis sabina. Both partially euryhaline and fully euryhaline species utilise the same physiological processes to control urea, Na+ and Cl- levels within the body fluids. The role of the gills, kidney, liver, rectal gland and drinking process is discussed in relation to the endocrine control of urea, Na+ and Cl- levels as elasmobranchs acclimate to different environmental salinities. (C) 2003 Elsevier Inc. All rights reserved.