Pumice is a porous volcanic rock containing a significant proportion of silica and alumina, and which has a low iron content. This natural, silica-rich material attracts wide attention because of its applications in adsorption processes, heterogeneous catalysis and nanotechnology. In this contribution, the white amorphous silica nanoparticles were extracted using an optimized alkaline treatment and an acid-precipitation process using grey pumice powder. The isolated amorphous silica SiO2 was characterized via X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electronic Microscopy (TEM-EDS), N2 adsorption/desorption measurements and simultaneous Thermal Gravimetry/Differential Thermal Analysis (TG/DTA). The obtained results indicated that the nanosilica powder was successfully prepared via the acid-base route with a predominantly amorphous mesoporous structure having a high surface area (422m2/g). The TEM images exhibited relatively homogeneous dispersed nanosilica particles with small sizes about 5–15 nm, in accordance with XRD data. Thermal analysis of the silica powder under air atmosphere showed total mass losses of 6.5%, with endothermic effects corresponding to the removal of water molecules and the OH of silanol groups contained in the material. The investigations performed in this work have indicated that there is great scope for pumice exploitation as a raw material in the production of amorphous silica nanopowder on large scale.

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been used for the first time to support ruthenium nanoparticles for the hydrogenation of p-chloronitrobenzene (p-CNB) to produce selectively p-chloroaniline. The preparation of well-dispersed ruthenium catalysts from the [Ru(3)(CO)(12)] precursor required activation of the purified supports by nitric acid oxidation. The supports, purified and functionalized, and the supported catalysts have been characterized by a range of techniques. The catalytic activity of these materials for the hydrogenation of p-CNB at 35 bar and 60 °C is shown to reach as high as 18 mol(p-CNB)g(Ru)(-1) h(-1), which is one order of magnitude higher than a commercial Ru/Al(2)O(3) catalyst. Selectivities between 92 and 94 % are systematically obtained, the major byproduct being aniline.

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This paper involves the investigation of the calcined Ca-hydroxyzincate dehydrate (CHZ) as solid base catalysts for photocatalytic degradation of methylene blue. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG-DTA), and UV-Vis spectroscopy were carried out to characterize and evaluate the as-prepared samples. The calcined catalysts performances were promising compared to non-calcined material. All the photocatalysts prepared under different processing temperatures (200, 400 and 600 °C) displayed 100% methylene blue degradation compared to the non-calcined sample with 100% dye removal.

This work establishes a simple method for synthesising layered double hydroxides (LDHs) powders with coprecipitation. The characteristics of the samples were investigated y X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectrophotometer UV–Vis (DRS). Non-uniform distribution was shown for LDHs samples by SEM. Photocatalytic efficiencies were tested using methylene blue (MB) dye as a model contaminant under UV irradiation. In particular, Zn–Al-Ti LDH exhibited an excellent performance towards MB degradation compared with commercial TiO2 nanoparticles. Methylene blue removal percentage was reached at almost 100%, whereas commercial TiO2 reached a removal rate of only 66% under the same conditions within 20 min. The aim of the current work is to prepare Zn-Al-Ti layered double hydroxides nanocomposite and to evaluate their photocatalytic activity in the removal of methylene blue under UV irradiation.

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