196,490 research outputs found
FUEL-BASED POLLUTANTS REMOVAL FROM WATER: STRUCTURAL EVIDENCES OF ADSORPTION INTO HIGH SILICA ZEOLITES
No full textThe enormous and rapid development of the chemical and agrochemical industries during the last century has resulted in the release of a large number of chemical compounds into the environment. Aquatic ecosystems are especially vulnerable because water bodies are frequently used, directly or indirectly, as recipients of potentially toxic liquids and solids from domestic, agricultural and industrial wastes. Removal of fuel-based compounds from natural water is of considerable interest due to the harmful effects of these pollutants on the environment, even at very low concentration [1]. Among this category of compounds, toluene, 1,2-dichloethane and methyl-tert-buthyl-ether are of special relevance since are toxic and commonly found in natural water. Research on hydrocarbon removal has been mainly focussed on single components from air matrix, whereas the studies involving aqueous dilute solutions are few [2-5]. Adsorption is a reliable alternative to eliminate these organic compounds from wastewaters because of the flexibility of the system, low energy and cheap operation costs. Moreover, the process does not induce the formation of oxidation intermediates which are, to date, mostly unknown. The presence of natural organic matter can significantly affect organic pollutant adsorption by either competing for adsorption sites, or restricting access to (micro)pores.
This work is a part of a wider project whose purpose is to study the interaction and mobility of ground water pollutants adsorbed in the zeolites pores. Organophilic synthetic zeolites which are cheap and available on the market, differing in topology, channel systems and free window apertures, and fuel-based-pollutants differing in chemical properties and molecular dimensions, were tested. In particular, structural evidences of adsorption from dilute solutions into organophilic zeolite as well as the competitive role of humic acid monomers, the effect of the temperature in the adsorption processes will be discussed. The selected adsorbents were commercial as-synthesized hydrophobic ZSM-5 and Y zeolites with high SiO2/Al2O3. Kinetics and adsorption isotherm batch data were obtained via Headspace Solid Phase Microextraction-GC. X-ray powders patterns were collected before and after adsorption on a Bruker D8 Advance diffractometer equipped with SOL-X detector. Thermal analyses (TG and DTA) were performed in air up to 900°C at 10°C/min. Infrared spectra were collected on a Thermo Electron Corporation FT Nicolet 5700 Spectrometer. This combined diffractometric, thermogravimetric, chromatographic and spectroscopic study allowed us to: 1) measure the sorption capacity of hydrophobic zeolite materials weighed against organic pollutants dissolved in water; 2) characterise the structure after contaminants adsorption; 3) localise the organic species in the zeolite channel systems; 4) highlight the role of humic acid monomers in the pollutants removal; 5) probe the interaction between the adsorbate and the zeolite framework. The very favorable adsorption kinetics along with the effective and highly irreversible adsorption into zeolite pores make these cheap and environmental friendly materials applicable for the treatment of water contaminated with fuel-based pollutants.
References. [1] Trindade P.V.O., Sobral L.G. , Rizzo A.C.L., Leite S.G.F. (2005) Chemosphere, 58, 515–522; [2] L.Abu-Lail, J. A. Bergendahl, R. W. Thompson, Journal of Hazardous Materials 2010, 178, 363-369. [3] Martucci A., Pasti L., Nassi M., Alberti A., Arletti R., Bagatin R., Vignola R., Sticca, R. (2012) Micropor. Mesopor. Mater. 148, 174-183. [4] Arletti, R., Martucci, A., Alberti, A., Pasti, L., Nassi, M., Bagatin, R. (2012) Journal of Solid State Chemistry, 194, 135-142.[5] Pasti L., Martucci A., Nassi M., Cavazzini A., Alberti A., Bagatin, R. (2012) Microporous and Mesoporous Materials, 160, 182-193
Consenso informato e tradizione islamica. Confronto culturale e legislativo a fini medico-legali.
No full textHigh-reliability fault tolerant digital systems in nanometric technologies: Characterization and design methodologies
No full textThis paper reports the main contribution of a project devoted to the definition of techniques to design and evaluate fault tolerant systems implemented using the SoPC paradigm, suitable for missionand safety-critical application environments. In particular, the effort of the five involved research units has been devoted to address some of the main issues related to the specific technological aspects introduced by these flexible platforms. The overall target of the research is the development of a design methodology for highly reliable systems realized on reconfigurable platforms based on a System-on-Programmable Chip (SoPC), as discussed in the next sectio
A new linear amplifier for the RFX electron energy analyzer
No full textA simple low cost novel linear amplifier has been developed for the electron energy analyzer employed on the reversed field pinch experiment RFX. The amplifier is designed to provide a 1 kV output voltage from a 10 V input. The current rating is ± 50 mA. It utilizes a configuration of four blocks in series, each of them with an output totem-pole configuration. The rise and fall times are of a few milliseconds. A fast protection against output short circuit has been implemented. The amplifier has been used in various experimental campaigns on RFX and multiple time resolved measurements of the edge electron energy distribution in a single plasma discharge have been obtained
The power supply system for Langmuir probes on RFX
No full textA power supply system for Langmuir probes to be used on the reversed field pinch (RFP) thermonuclear fusion experiment RFX has been developed. It is based on a full-bridge converter concept, using a pulse width modulation (PWM) technique, and is characterized by a 5 A, ±150 V rating. The power supply has been designed to ensure compatibility with the electromagnetic noise close to the machine and with the plasma, which behaves as a nonlinear rapidly varying load. The system has been optimized by numerical simulations. Tests in the laboratory and on the experiment have been performed in a wide range of working conditions, and the system has been proven to suit fairly well the RFX experimental conditions
Risparmio energetico negli edifici: valutazioni economiche delle alternative di isolamento termico
No full textViene presentata una metodologia che permette di individuare la combinazione ottimale, dal punto di vista economico, degli interventi migliorativi dell'isolamento termico delle diverse superfici dell'involucro di un edificio. L'ottimizzazione economica degli interventi è condotta in riferimento a due casi tipici. Nel primo si cerca di rendere minima la spesa dei materiali coibenti nel caso sia fissalo a priori il coefficiente volumico di dispersione. Nel secondo caso si determina il grado di isolamento che rende massimo il valore attuale netto dell'investimento in relazione al risparmio di combustibile ottenibile nel corso della vita dell'immobile. La trattazione si avvale di un modello analitico adatto per edifici in progettazione e di una procedura a valori discreti applicabile agli edifici esistenti
Soft errors in floating gate memory cells: A review
No full textSoft errors due to neutrons and alpha particles are among the main threats for the reliability of digital circuits operating at terrestrial level. These kinds of errors are typically associated with SRAMs and latches or DRAMs, and less frequently with non-volatile memories. In this paper we review the studies on the response of NAND and NOR Flash memories to ionizing particles, focusing on both single-level and multi-level cell architectures, manufactured in technologies down to a feature size of 25 nm. We discuss experimental error rates obtained with accelerated tests and identify the relative importance of neutron and alpha contributions. Technology scaling trends are finally discussed and modelled. © 2014 Elsevier Ltd. All rights reserved
Boron removal from water: Needs, challenges and perspectives
No full textBoron is often present in water streams to be treated to match final user specifications or environmental restrictions. It can not be removed by conventional water treatments and its separation still remains an issue. An overview on this topic is provided. Needs are identified considering information regarding boron level effect on environment, human health and activities. Challenges are described envisaging boron main physical-chemical properties and current approaches for its removal. Perspectives are sketched pointing to possible technology improvements
Enhancements in ElectroKinetic Remediation Technology: Focus on hydraulic management and wastewater recovery
No full textThe ElectroKinetic Remediation Technology (EKRT), when applied to an earthy matrix, is generally targeted to the extraction of one or more pollutants, often inorganic and typically belonging to the category of heavy metals. The technique exploits the effects caused by the application of an electric field for allowing the mobilization of the targeted pollutants, whose displacement is often facilitated by the use of suitable chemicals, which act as complexing agents. The EKRT represents a very promising approach, as it is able to produce results comparable to those of other on/off-site interventions, though with appreciably higher levels of acceptability. Moreover, in spite of expectations (which are substantially based on the high use of energy and consumables), we showed that, once properly configured, the EKRT may represent an excellent choice even when judged based on the environmental sustainability. With the present study, we aim at discussing further the plant configuration, with a special focus on the water management. In fact, as anticipated in our previous communications, the modifications that we implemented in our EKRT approach allow presenting it as an electrochemically-assisted soil flushing. Several are the elements of innovation introduced, which proved to increase the effectiveness of the remediation, but at the price of a potentially very high water (and energy) consumption. It is therefore important to have an advanced water management system, preferably coupled with a reliable wastewater recovery system in order to avoid the waste of water resources, and consequently keep down costs as well as the ecological footprint related with the implementation of this technology, thus maximizing its benefits
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