1,720,991 research outputs found
Screening di materiali tramite ICP-MS per caratterizzazione di background in esperimenti di bassa radioattività
No full textSearch for very rare astroparticle physics events, such as Neutrinoless Double Beta
Decay or direct Dark Matter interactions demands for extremely low background
environments and materials for the experiment construction. The former requirement
is fulfilled by underground laboratories, such as the Laboratori Nazionali del Gran
Sasso of INFN, where the overburden rock reduces the cosmic ray flux by six orders
of magnitude with respect to the sea level. The latter requirement, i.e., the material
selection and cleaning for low-background experiment, increasingly challenges the
international scientific community to develop new purification techniques and push
the sensitivity to the edge of instrumental limits. Indeed, given the variety of
materials used for the construction of experiments (i.e., metals, plastics, electronics
compounds, loaded liquids, pressurised gases) and the very low levels of radiocontamination required, versatile and cutting-edge purification and characterisation
techniques are needed.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is one of the most
suitable technique for material screening because of its versatility and additional
features such as high sensitivity (ppt level), short analysis time (days), small mass of
samples (mg), possibility to acquire many elements simultaneously, and development
of efficient analysis methods. Furthermore, several processes and chemical treatments
are involved in the production of the raw materials, thus the effect of each step on the
final product must be known in detail in order to be able to optimize the production
protocol from the radiopurity point of view. ICP-MS is the only screening technique
capable of investigating contaminations in all stages of production, for example
separating bulk contaminations from surface ones by means of progressive chemical
attacks.
In order to reach excellent results with ICP-MS, the workspace is crucial, because
environmental contaminations must be avoided. For this reason, clean-rooms are
ideal environment to perform both sample’s treatment and characterization through
ICP-MS.
My thesis work was developed at the Chemistry and Chemical Plants Service
of the Gran Sasso National Laboratories. I was involved in the development of
innovative techniques for the cleaning and characterization of materials. Especially
of the X and Y experiments.
In the framework of the LEGEND experiment, highly enriched germanium
crystals have been purified exploiting a chemical plant designed for this specific
purpose. A sequence of chemical reactions was tuned to convert metal germanium
crystals into high pure GeO2. The purification process was continuously monitored
online by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), in order to
verify the purification efficiency and the conversion rate from starting material to
final products.
Moreover, another material widely used to build inner structures and external
shields of astroparticle physics experiments is copper, which is one of the most
radiopure metal, easy to machine and suitable also for cryogenic applications. Given
the extremely low contaminations in thorium and uranium (10−12 – 10−15 g/g) in
copper, different approaches must be developed in order to reach low detection limits
at a level of 0.4 - 1 × 10−12 g/g). In this thesis, pre-concentration methods based on
matrix extractions were developed to maximize quantification of Th and U in several
samples of copper. On the other hand, also different materials (plastic, metals,
organic) have been characterized through ICP-MS analysis, developing different
treatments to solubilize them
Oil refining spent catalysts: A review of possible recycling technologies
No full textThe aim of this review paper is to analyse the current management of spent fluid catalytic cracking catalysts (FCCCs) and the relevant possible reuse and recycling methods in order to avoid landfilling. FCCCs are used in refining processes for conversion of vacuum gas oil into more valuable gasoline blend components and other products. Every year the worldwide supply is estimated at about 840,000 t (Letzsch, 2014). The main recycling technique found in literature for spent FCCCs entails their use as raw material for concrete and mortar production as partial replacement of sand and cement powder. Other minor applications include their use as catalysts for plastic and biomass pyrolysis and gasification or for production of synthetic fuels. Despite their importance, these processes have not been widely developed at industrial scale. Disposal to landfill or use for concrete blend is still the main choice for the handling of spent catalysts, despite the content of rare earths elements and sometimes other interesting metals like vanadium and nickel that could be recovered. Nevertheless, in the future these catalysts will represent an interesting source for secondary raw materials, considering the scarcity of rare earth elements and shortage of supply, due to the fact that production is concentrated only in few countries. In this perspectives, the recovery of rare earth elements will be of great interest to countries that do not own primary ores. Future research work is expected to lead to economical processes that reach a complete recycling in order to avoid landfilling. This action could be helped by the adoption of new environmental regulations which will heavily charge landfilling as final disposal
The case study of a photovoltaic plant located at the university of L’Aquila: An economic analysis
No full textSolar energy has contributed significantly to the energy transition towards a low carbon society. Public offices – including universities – are being called to participate in the solar energy transition, as the availability of their rooftops represents an opportunity. The present study aimed at evaluating the economic feasibility of a photovoltaic (PV) plant at the University of L’Aquila, approximately 10 years after an earthquake devastated the region. The reconstruction process is ongoing, and a solar PV plant could potentially move the city in a sustainable direction. The development of sustainability models requires the economic verification of relevant projects and a complete list of indicators for decision-makers. The present work found that a 210 kW PV plant at the University of L’Aquila would reduce emissions by 184.9 t CO2eq/year and generate 1500 € profits for each kW installed; and a 115 kW PV plant would reduce emissions by 101.5 t CO2eq/year and generate profits of 1370 € for each kW installed. The analysis of alternative scenarios gave solidity to the results, confirming the pivotal role of the share of self-consumed energy. Level of insolation and plant size were also found to significantly influence economic performance. Finally, the adoption of a bonus to encourage the production and self-consumption of energy may increase investors’ attention towards environmental issues
Treatment of fluid catalytic cracking spent catalysts to recover lanthanum and cerium: Comparison between selective precipitation and solvent extraction
No full textRare earths from secondary sources: profitability study
No full textThe paper is focused on the economic analysis of two hydrometallurgical processes for recovery of yttrium and other rare earth elements (REEs) from fluorescent phosphors of spent lamps. The first process includes leaching with sulphuric acid and precipitation of a mixture of oxalates by oxalic acid, the second one includes leaching with sulphuric acid, solvent extraction with D2EHPA, stripping by acid and recovery of yttrium and traces of other rare earths (REs) by precipitation with oxalic acid. In both cases the REEs were recovered as oxides by calcination of the oxalate salts. The economic analysis was estimated considering the real capacity of the HydroWEEE mobile's plant (420 kg batch(-1)). For the first flow-sheet the cost of recycling comes to 4.0 (sic) kg(-1), while the revenue from the end-product is around 5.40 (sic) kg(-1). The second process is not profitable, as well as the first one, taking into account the composition of the final oxides: the cost of recycling comes to 5.2 (sic) kg(-1), while the revenue from the end- product is around 3.56 (sic) kg(-1). The process becomes profitable if the final RE oxide mixture is sold for nearly 50 (sic) kg(-1), a value rather far from the current market prices but not so unlikely since could be achieved in the incoming years, considering the significant fluctuations of the Res' market
Separation of carbon dioxide for biogas upgrading to biomethane
No full textThe present paper deals with carbon dioxide capture from dry CO2/CH4 mixtures by means of zeolites produced from spent power plant fly ash. Commercial sorbents such as activated carbon, silica gel and zeolite 13X were also tested. At an operating pressure of 2 bar, the best zeolite synthesized in this work gave rise to recoveries of CH4 and CO2 of 95.2% and 98.1% respectively, at purities of 98 vol% and 99.6 vol% respectively. Among the commercial sorbents tested at 2 bar pressure, the best one was silica gel, with recoveries of CH4 and CO2 of 85.4% and 97.6% respectively at purities of 97.3 vol% and 94.9 vol% respectively. At this pressure, the CO2 adsorption rate was 0.402 moL/kg silica sorbent; at 6 bar this increased to 1.076 mol CO2/kg silica sorbent but at greatly reduced levels of both CH4recovery and CO2 purity. Three zeolites produced from fly ash also underwent PSA (Pressure Swing Adsorption) tests: after five adsorption-desorption cycles no loss in adsorption capacity of CO2 was observed, both activity and selectivity recovering completely after regeneration
Secondary yttrium from spent fluorescent lamps: Recovery by leaching and solvent extraction
No full textThe separation of yttrium and calcium from acid leach liquor obtained from leaching of fluorescent lamp phosphors has been investigated by solvent extraction with D2EHPA and Cyanex 272 in kerosene. The preliminary tests suggested that D2EHPA was more efficient than Cyanex 272 for separation of yttrium. The experimental tests allowed to define the best process conditions, among those investigated, to separate and recover yttrium selectively. The best separation circuit included three-stage cross current extraction with 20%v/v D2EHPA in kerosene (O/A = 1/1, room temperature, 10 min of contact, pH 0.02) and stripping step in counter current with 1.5 M sulfuric acid (O/A = 1/1, room temperature, 30 min of contact). After stripping, yttrium was recovered as oxalate by the addition of oxalic acid. According to the experimental results, a hydrometallurgical process was developed. The final recovery from leach liquor was around 90% and the grade of the final product was 97.5% as hydrated yttrium oxalate. The main impurity was sulfur, 1.28% wt, in addition to traces of other elements such as Si (0.057% wt), Zn (0.015% wt), Eu (0.14% wt) and Fe (0.02% wt)
Separation and recovery of glass, plastic and indium from spent LCD panels
No full textThe present paper deals with physico-mechanical pre-treatments for dismantling of spent liquid crystal displays (LCDs) and further recovery of valuable fractions like plastic, glass and indium. After a wide experimental campaign, two processes were designed, tested and optimized. In the wet process, 20%, 15% and 40% by weight of the feeding panels are recovered as plastic, glass and indium concentrate, respectively. Instead, in the dry process, only two fractions were separated: around 11% and 85% by weight are recovered as plastic and glass/indium mixture. Indium, that concentrated in the â212 Î1⁄4m fraction, was completely dissolved by sulphuric acid leaching (0.75 mol Lâ1H2SO4solution, 80 °C, 10%vol H2O2, pulp density 10%wt/vol, leaching time 3 h). 100% of indium can be extracted from the pregnant solution with 5%wt/vol Amberlite⢠resin, at room temperature and pH 3 in 24 h. Indium was thus re-extracted from the resin by means of a 2 mol Lâ1H2SO4solution, at room temperature and S/L of 40%wt/vol
Assessing the recyclability of spent fluid catalytic cracking catalyst for sustainable dry reforming of methane
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