Elza Bontempi

Review of fly ash inertisation treatments and recycling

Fly ash (FA) is a by-product of power, and incineration plants operated either on coal and biomass, or on municipal solid waste. FA can be divided into coal fly ash, obtained from power plant burning coal, flue gas desulphurisation FA, that is, the by-product generated by the air pollution control equipment in coal-fired power plants to reduce the release of SO2, biomass FA produced in the plants for thermal conversion of biomass and municipal solid waste incineration (MSWI) FA, that is, the finest residue obtained from the scrubber system in a MSWI plant. Because of the large amount produced in the world, fly ash is now considered the world’s fifth largest material resource. The composition of FA is very variable, depending on its origins; then, also pollutants can be very different. In this frame, it is fundamental to exploit the chemical or physical potentials of FA constituents, thus rendering them second-life functionality. This review paper is addressed to FA typology, composition, treatment, recycling, functional reuse and metal and organic pollutants abatement. Because of the general growing of environmental awareness and increasing energy and material demand, it is expected that increasing recycling rates will reduce the pressure on demand for primary raw materials, help to reuse valuable materials which would otherwise be wasted and reduce energy consumption and greenhouse gas emissions from extraction and processing.

Flexible dye sensitized solar cells using TiO2 nanotubes

The growth of TiO2 nanotube arrays on plastic flexible substrates is researched. The approach uses anodization of a titanium thick film for obtaining nanotubes directly on poly(ethylene terephthalate) (PET) and Kapton HN substrate. The morphological features of the tubes can be finely tuned by varying the preparation conditions, and tube morphology affects the functional properties of the nanotube array. Crystallization of the anatase phase in nanotubes on Kapton HN substrate is obtained via post growth annealing. The nanotube arrays have been dye-sensitized using the commercial Ru-based N719 dye. The system was tested as photoanode in a flexible dye sensitized solar cell. Photoconversion efficiency of 3.5% was obtained.

Tailoring the Pore Size and Architecture of CeO2/TiO2 Core/Shell Inverse Opals by Atomic Layer Deposition

Hierarchically ordered porous materials have been receiving attention because of their large number of applications in several fields of materials science, including catalysis, optoelectronics, molecular sieves, drug delivery, and electrodes for fuel, solar, and thermophotovoltaic cells. Among the variety of templating agents for preparing organized mesostructures, colloidal crystals are widely used to generate twoand threedimensional (2D and 3D) photonic-bandgap materials, which exhibit Bragg diffraction within frequency ranges for which light propagation through the material is forbidden. Stopband reflections have been recently proposed to be exploited in the field of photocatalysis. Indeed, it has been demonstrated that, at the frequency edges of these stop bands, photons propagatewith strongly reduced group velocity. If the energy of these slow photons overlaps with the absorbance of the material, the effective optical path length is significantly enhanced, thus improving the catalytic activity of the system. Recently, Chen et al. demonstrated that the photoactivity of anatase TiO2 inverse opals is remarkably enhanced by using slow photons with energies close to the electronic bandgap of the semiconductor. In a following paper, the same authors demonstrated that a certain degree of microstructural disorder, which is inherently associated with these materials, can be tolerated without preventing their use in some important applications, such as purification of water from environmental pollutants (dyes, viruses, etc.). In addition, Mallouk and co-workers and, more recently, Corma and coworkers investigated the use of the photonic crystal topology for photoelectrochemical solar cells. TiO2 inverse opals exhibited a conversion efficiency of light that is five times higher than that of nonphotonic crystal reference samples.

Vertically Aligned TiO2 Nanotubes on Plastic Substrates for Flexible Solar Cells

Electrochemical anodization of a titanium film on a Kapton HN substrate leads to the formation of closely packed aligned nanotubes, whose shape can be finely tuned by tailoring the anodization parameters. An amorphous-to-anatase phase transition is induced on nanotubes by annealing at 350 °C. The nanotubes are applied as photoanodes in flexible dye-sensitized solar cells (N719 dye; I3-/I- redox couple), resulting in a photoconversion efficiency of up to 3.5% under simulated sunlight irradiation air mass 1.5 global (AM 1.5G).

Total reflection of x-ray fluorescence (TXRF): a mature technique for environmental chemical nanoscale metrology

Total reflection x-ray fluorescence (TXRF) is a technique well established for chemical analysis of samples deposited as a thin layer. Nowadays it is mainly employed for electronic industry quality control. Recently, very compact and economic TXRF instrumentation was proposed. Combining this with the capability to analyze liquid samples, this technique is suitable to be employed in many different applications, comprising the very critical field of environmental analysis. Comparisons with the standard atomic absorption spectroscopy (AAS) technique show that TXRF is a practical, accurate, and reliable technique. Indeed, round-robin activities have already been started. Despite the efficiency and economy of the developed portable TXRF instrumentation, this is not widely employed for chemical laboratory analysis probably because TXRF is not an officially recognized technique, i.e. it is not yet normative-subjected. This fact could also be due to the long background of analytical applications developed for AAS, ICPS or inductively coupled plasma mass spectroscopy (ICP-MS) up to now. In this paper, we present a work of environmental monitoring of an industrial site, performed by means of bioindicators (lichens). The analysis of trace elements concentration in lichen was usually conducted with spectrophotometric techniques, such as AAS and ICP-MS, which were accepted by common regulations and normative-subjected. In this study, we accomplished a comparative lichen analysis by AAS and TXRF. The reproducibility of the obtained results showed the high correspondence between the two techniques. This comparison highlighted the versatility of the TXRF apparatus that allowed more rapid and simultaneous element detection. The obtained results suggested that this portable TXRF system could be suitable for regulation to produce certificated analysis upto ppb concentrations for some elements.

Vapor Phase Processing of α-Fe2O3 Photoelectrodes for Water Splitting: An Insight into the Structure/Property Interplay

Harvesting radiant energy to trigger water photoelectrolysis and produce clean hydrogen is receiving increasing attention in the search of alternative energy resources. In this regard, hematite (α-Fe2O3) nanostructures with controlled nano-organization have been fabricated and investigated for use as anodes in photoelectrochemical (PEC) cells. The target systems have been grown on conductive substrates by plasma enhanced-chemical vapor deposition (PE-CVD) and subjected to eventual ex situ annealing in air to further tailor their structure and properties. A detailed multitechnique approach has enabled to elucidate the interrelations between system characteristics and the generated photocurrent. The present α-Fe2O3 systems are characterized by a high purity and hierarchical morphologies consisting of nanopyramids/organized dendrites, offering a high contact area with the electrolyte. PEC data reveal a dramatic response enhancement upon thermal treatment, related to a more efficient electron transfer. The reasons underlying such a phenomenon are elucidated and discussed by transient absorption spectroscopy (TAS) studies of photogenerated charge carrier kinetics, investigated on different time scales for the first time on PE-CVD Fe2O3 nanostructures.

Morphology and microstructural properties of TiO2 nanopowders doped with trivalent Al and Ga cations

The effects of doping on the morphological and microstructural properties of TiO2 nanopowders produced by laser pyrolysis were investigated mainly by x-ray diffraction (XRD) and electron microscopy. Samples of TiO2 powders were prepared by doping with different trivalent cations (Al and Ga). The powders were calcined at different temperatures in the range 400–1000 °C for 18 h, as well as at constant T = 700 °C up to 160 h. After each thermal treatment, XRD patterns were collected. The analysis of XRD patterns allowed us to estimate the microstrains and average crystallite size and to observe the evolution of the microstructural parameters with temperature. Both Al and Ga inhibited the crystallite growth of TiO2 anatase and the rutile phases, this effect being larger in the Al-doped powders.

Niobium-titanium oxide powders obtained by laser-induced synthesis: Microstructure and structure evolution from diffraction data

The influence of the niobium content on the anatase-to-rutile phase transition in nanopowders of Nb–Ti oxides was studied and the changes in the particle size and microstrain distribution obtained at different temperatures were analyzed. A correlation is found between the initial microstructure in the Ti 1 – x Nb x O 2 ( x = 0.03, 0.2) powder and the niobium content. The presence of Nb was found to inhibit the growth of both the anatase and the rutile phases.

Fabrication and investigation of gas sensing properties of Nb-doped TiO(2) nanotubular arrays.

Synthesis of Nb-containing titania nanotubular arrays at room temperature by electrochemical anodization is reported. Crystallization of pure and Nb-doped TiO(2) nanotubes was carried out by post-growth annealing at 400°C. The morphology of the tubes obtained was characterized by scanning electron microscopy (SEM). Crystal structure and composition of tubes were investigated by glancing incidence x-ray diffraction (GIXRD) and total reflection x-ray fluorescence (TXRF). For the first time gas sensing characteristics of Nb-doped TiO(2) nanotubes were investigated and compared to those of undoped nanotubes. The functional properties of nanotubular arrays towards CO, H(2), NO(2), ethanol and acetone were tested in a wide range of operating temperature. The introduction of Nb largely improves conductivity and enhances gas sensing performances of TiO(2) nanotubes.

Neurofunctional dopaminergic impairment in elderly after lifetime exposure to manganese.

BACKGROUND Manganese (Mn) is an essential element that can become neurotoxic through various exposure windows over the lifespan. While there is clear evidence of Mn neurotoxicity in pediatric and adult occupational populations, little is known about effects in the elderly who may exhibit enhanced susceptibilities due to compromised physiology compared to younger adults. In the province of Brescia, Italy, the Valcamonica area has been the site of three ferroalloy plants operating from 1902 to 2001. Metal emissions of Mn and to a lesser extent lead (Pb) have impacted the surrounding environment, where a high prevalence of Parkinsonism was previously observed. This study aimed to assess neurocognitive and motor functions in healthy elderly subjects residing for most of their lifetime in Valcamonica or in a reference area unimpacted by ferroalloy plant activity. METHODS Subjects were enrolled for extensive neurobehavioral assessment of motor, cognitive and sensory functions. Exposure was assessed with 24h personal air sampling for PM10 airborne particles, surface soil and tap water measurement at individual households, Mn levels in blood and urine and Pb in blood. Dose-response relationships between exposure indicators and biomarkers and health outcomes were analyzed with generalized (linear and logistic) additive models (GAM). RESULTS A total of 255 subjects (55% women) were examined; most (52.9%) were within the 65-70 years age class. Average airborne Mn was 26.41 ng/m(3) (median 18.42) in Valcamonica and 20.96 ng/m(3) (median 17.62) in the reference area. Average Mn in surface soil was 1026 ppm (median 923) in Valcamonica and 421 ppm (median 410) in the reference area. Manganese in drinking water was below the LDL of 1 μg/L. The GAM analysis showed significant association between airborne Mn (p=0.0237) and the motor coordination tests of the Luria Nebraska Neuropsychological Battery. The calculation of the Benchmark Dose using this dose-response relationship yielded a lower level confidence interval of 22.7 ng/m(3) (median 26.4). For the odor identification score of the Sniffin Stick test, an association was observed with soil Mn (p=0.0006) and with a significant interaction with blood Pb (p=0.0856). Significant dose-responses resulted also for the Ravens Colored Progressive Matrices with the distance from exposure point source (p=0.0025) and Mn in soil (p=0.09), and for the Trail Making test, with urinary Mn (p=0.0074). Serum prolactin (PRL) levels were associated with air (p=0.061) and urinary (p=0.003) Mn, and with blood Pb (p=0.0303). In most of these associations age played a significant role as an effect modifier. CONCLUSION Lifelong exposure to Mn was significantly associated with changes in odor discrimination, motor coordination, cognitive abilities and serum PRL levels. These effects are consistent with the hypothesis of a specific mechanism of toxicity of Mn on the dopaminergic system. Lead co-exposure, even at very low levels, can further enhance Mn toxicity.