Facile synthesis of high-surface-area nickel-based mixed-metal oxides with interconnected mesopore networks through a novel layered double hydroxide/carbon (LDH/C) hybrid composite precursor route is successfully established. The starting LDH/C composite with interwoven framework structure is assembled by the crystallization of Ni/Al layered double hydroxide simultaneously accompanied by the carbonization of glucose under mild hydrothermal conditions, and subsequently, the formed composite is thermally decomposed to generate mesoporous nickel-based mixed-metal oxides after removal of the carbon. The materials have been characterized by X-ray diffraction (XRD), Fourier transform infrared technique (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen sorption measurements. The results elucidate that the specific surface area of calcined LDH/C composite at 450 °C can be as high as 288 m2 g−1, and decreases gradually with the calcination temperature. The effect of in situ generated carbon as template in the composite precursor is an essential factor to direct the formation of the high-surface-area mixed oxides with interconnected mesopore network. And the porosity of the obtained solids can be dominated by adjusting the calcination temperature of precursors. Furthermore, through catalytic investigations, these as-prepared high-surface-area Ni-based mixed oxides display excellent catalytic activities for the growth of carbon nanotubes in chemical vapor deposition reactions.

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The controlled growth of three types of carbon nanostructures (tubes, caterpillar-like fibers and interwoven spheres) was successfully achieved via the catalytic chemical vapor deposition of acetylene, using an effective, silicon supported catalyst derived from a Co-Al layered double hydroxide precursor. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the grown carbon nanostructures can be tuned by adjusting the duration of catalytic growth. Short growth duration of 20 min produces uniform carbon nanotubes, while long growth durations of 40 and 60 min result in the formation of caterpillar-like fibers and interwoven spheres, respectively. The growth mechanism of these structures is discussed on the basis of an overgrowth of the initially formed tubular carbon nanostructures. Furthermore, the morphology of the obtained carbon nanostructures has considerable effect on their wettability. Particularly, the as-grown caterpillar-like carbon fibers and interwoven spheres over the surface of the substrate exhibit rather high water contact angles of 163 AE 2 and 168 AE 2 , respectively. This indicates excellent surface super-hydrophobic properties, which originate from the uniqueness of their surface structures.

Le charbon actif élaboré à partir de biomasses lignocellulosiques est une bonne voie de valorisation de déchets, vue ses applications. Ce travail porte sur l'élaboration du charbon actif à partir de Balanites aegyptiaca par activation chimique à l'acide ortho phosphorique, son application pour éliminer le chrome VI en solution. La concentration de l'acide, le temps d'imprégnation, la température de pyrolyse et le palier d'isotherme ont été variés. La caractérisation a porté sur la détermination des indices d'iode et de bleu de méthylène, des fonctions de surface et de pH au point de charge nulle (pH PCN). Le temps de contact, le pH du milieu, la masse de l'adsorbant et la concentration initiale de la solution ont été variés pour l'élimination du chrome. Les meilleurs indices d'iode et de bleu de méthylène obtenus sont : 989,86 mg/g et 613,17 mg/g respectivement. Les fonctions à la surface des charbons actifs sont de nature acide et leur pH PCN inférieur à 7. Le rendement d'élimination du chrome varie de 81,64% à 98,77% dans les conditions : concentration initiale (70 mg/L), pH = 2, masse (80 mg) et temps (2 h). A titre de comparaison, le charbon actif commercial de marque KGA a donné un taux de rabattement en chrome de 91,49%.

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