1,721,082 research outputs found
THE CONCEPT OF END OF WASTE IN VIEW OF DEVELOPING SUSTAINABLE SECONDARY RAW MATERIALS
No full textThe concept of end of waste, adopted by the European Commission on December 2005, regards under which conditions a waste could cease to be waste and could be regarded as a non-waste material. This is a revolutionary way to think of wastes not just as refuse to be dismissed but as secondary raw material to be exploited, with an enormous social and economic impact. In this scenario, the creativity of materialsscientists is highly stimulated and the key to success is the development of innovative and sustainable means to transform a waste into a secondary raw material of potential economic value. To this aim, stimulus comes from the so called geo-inspiring materials. This contribution presents the results of a long-term project aimed to recycle asbestos containing materials (ACMs), into secondary raw materials for various industrial applications. The high temperature product of transformation of ACM can be successfully recycled in clay bricks, rock-wool, glass–ceramics, ceramic pigments[1], geopolymers [2], concrete [3], and recently also for innovative formulations of calcium sulfoaluminate cement clinkers [4 ] and magnesium phosphate cements [5]
In-situ/operando characterization of FeOx-based chemiresistive sensor of acetone vapours by X-ray absorption spectroscopy
Full text linkIsoprene improves photochemical efficiency and reduces heat dissipation in plants at physiological temperatures
No full textPotentially toxic elements speciation in bottom ashes from a municipal solid waste incinerator: A combined SEM-EDS, μ-XRF and μ-XANES study
Full text linkBottom Ashes from Municipal Solid Waste Incinerators and Waste to Energy plants represent an interesting source of secondary raw materials for many applications, like urban mining and inclusion in concrete, and road pavement. However, Bottom Ashes may contain potentially toxic elements, whose actual toxicity depends essentially on their oxidation state and mineralogical environment. For this reason, a representative sample of bottom ashes from Parma Waste to Energy plant has been selected to investigate the chemical speciation of Cr, Ni, Pb, Co, Zn and Cu by means of complementary techniques: Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), micro X-Ray Fluorescence (μ-XRF) mapping and X-Ray Absorption Near Edge Structure (XANES) measurements by synchrotron radiation. This multi-technique approach allowed to obtain a general image of the mineralogical and chemical environment in which these elements are found. SEM-EDS analyses show the presence of Zn and Pb both in minerals and in glass matrix. Cr has been detected in the form of oxide and in spinel structure (chromite) whereas Co and Cu are found as alloy or metal inclusions. μ-XRF mapping reveals that Cu, Ni and Cr are generally associated to Na, K and Si suggesting their presence in glass matrix. XANES investigations exhibit that Cu has a variable oxidation state that suggesting its presence in the form of oxide, hydroxide, acetate and metal. Zn is mainly found as +II and in a number of different phases (including Zn-carbonates, in agreement with SEM-EDS data). Cr has been found only as +III, with XANES features resembling those of chromite, whereas as +VI was never identified. Ni and Co were found either as metal form and oxides. Pb spectra show a good match with oxides
Volatile isoprenoids and their importance for protection against environmental constraints in the Mediterranean area
No full textAmong plant secondary metabolites, volatile isoprenoids have received increasing attention because they are involved in a range of physiological and ecological interactions, often helping plants cope with abiotic and biotic stressors, and potentially affecting the chemistry of the troposphere once they are emitted in the air. We review evidence about the beneficial functions of volatile isoprenoids in leaves, principally as antioxidants and membrane stabilizing agents, avoiding heat damage. Because the Mediterranean environment is characterized by prolonged dry and hot seasons, and recurrent heat-waves, we surmise that volatile isoprenoids are particularly widespread, and play an important physiological role, in Mediterranean woody plants. Based on a review of available inventories, isoprene emission characterizes deciduous woody plants, whereas evergreens are more often monoterpene emitters. Monoterpene emitters may be better fit to the Mediterranean climate, and, in general, to climate conditions favoring evergreens. © 2013 Elsevier B.V
Structural defects responsible for the strain glassy transition in Ni50+x Ti50-x
No full textThe strain glassy phase is produced by doping a small percentage of impurity in a martensitic alloy. Its ground state is conceived to consist of martensitic nanodomains spatially separated from each other by a defect phase. The present study, by probing the local structure around the Ni and Ti in martensitic and strain glassy compositions of Ni50+xTi50-x, identifies the defect phase that is responsible for inhibiting the long range ordering of the elastic strain vector leading to the formation of the strain glassy phase
Solubilization and coordination of the HgCl2 molecule in water, methanol, acetone, and acetonitrile: an X-ray absorption investigation
No full textX-ray absorption spectroscopy (XAS) has been employed to carry out structural characterization of the local environment around mercury after the dissolution of the HgCl2 molecule. A combined EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) data analysis has been performed on the Hg L3-edge absorption spectra recorded on 0.1 M HgCl2 solutions in water, methanol (MeOH), acetone and acetonitrile. The Hg-Cl distance determined by EXAFS (2.29(2)-2.31(2) Å) is always comparable to that found in the HgCl2 crystal (2.31(2) Å), demonstrating that the HgCl2 molecule dissolves in these solvents without dissociating. A small sensitivity of EXAFS to the solvent molecules interacting with HgCl2 has been detected and indicates a high degree of configurational disorder associated with this contribution. XANES data analysis, which is less affected by the disorder, was therefore carried out for the first time on these systems to shed light into the still elusive structural arrangement of the solvent molecules around HgCl2. The obtained results show that, in aqueous and MeOH solutions, the XANES data are compatible with three solvent molecules arranged around the HgCl2 unit to form a trigonal bipyramidal structure. The determination of the three-body Cl-Hg-Cl distribution shows a certain degree of uncertainty around the average 180° bond angle value, suggesting that the HgCl2 molecule probably vibrates in the solution around a linear configuration
Transformations through pseudomorphosis of asbestos minerals in thermally processed asbestos-containing materials investigated through SEM/EDS and micro-Raman spectroscopy: implications for recycling of hazardous wastes
No full textAsbestos-containing materials, extensively used in the past in many European countries, are now considered hazardous wastes of great concern. It has been proved that inertization can be obtained via thermal treatment above 1100 °C. This solution relies upon the scientific evidence that all asbestos minerals at high temperature transform into stable crystalline silicates via a solid state recrystallization process [1]. Asbestos fibres preserve the same external crystal habit although a complete modification of the structure at a molecular scale occurred. This phenomenon is called pseudomorphosis. With increasing the temperature of the thermal treatment above 650-750 °C, the transformation sequence of chrysotile asbestos predicts the crystallization of forsterite (Mg2SiO4) and enstatite (MgSiO3 ) [1]. In a system high in Ca, such as cement-asbestos, crystallization of cement phases such as larnite (Ca2SiO4), ferrite (ideally Ca4Al2Fe2O10), and Al-,Ca-,Mg-rich silicates, such as akermanite (ideally Ca2MgSi2O7) and merwinite (ideally Ca3MgSi2O8), occurs. In this work, analytical and spectroscopic techniques coupled with microscopy allowed for the study of individual residual pseudo-morphosed fibre bundles, in cement-asbestos samples heat treated at 1200 °C. Phases detected were mainly monticellite (CaMgSiO4) or akermanite. They likely formed through the reactions: CaO + MgSiO3 (en) -> CaMgSiO4 (mtc), and CaMgSiO4 (mtc) + CaO + SiO2 -> Ca2MgSiO7 (ake). This suggests that, although transformation reactions occurred largely at the solid state, a substantial mobilisation of Ca and Mg resulted. Such a process is essential for the attainment of the bulk mineralogical composition predicted by the phase diagrams in the system CaO-MgO-SiO2 [2]; however, because of crystallization under non equilibrium conditions, departures from the expected bulk phase composition are still observed. This study contributes to the definition of factors conditioning the recycling of transformed cement-asbestos as secondary raw material [2-3]
Investigation of setting reaction of magnesium-potassium phosphate ceramics by qualsi-elastic neutron scattering
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