Literatura académica sobre el tema "Iode – Isotopes – Absorption et adsorption"
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Tesis sobre el tema "Iode – Isotopes – Absorption et adsorption"
Morais, Andrade Pedro Henrique. "Interactions hôte-invité entre l'iode gazeux et les matériaux de type MOF : dynamique et réactivité". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILR094.
Texto completoThis work describes the synthesis and properties of three families of MOF materials (UiO-6x, MIL-125, CAU-1) used to trap iodine molecules. A first study investigates charge transfer complexes between iodine molecules and MOF frameworks upon adsorption, finding that hafnium-based UiO-66 compounds showed enhanced iodine uptake and transformation into I3-. In this case, a mechanism involving electron transfer from the organic linker to iodine was proposed. Using single crystals of UiO-67(Zr,Hf)_NH2 and taking advantage of Raman resonance effect, the higher stability of the I3- species was put forward by performing Raman mapping. Crystal size was shown to significantly affect iodine adsorption kinetics. In comparison to their aluminum-based structural analogue, MIL-125(Ti) and MIL-125(Ti)_NH2 MOFs demonstrated faster iodine adsorption kinetics due to efficient charge separation. In this case, thermal desorption experiments showed the stability of I3- species, particularly in the presence of -NH2 groups. Moreover, contrary to what is observed for zirconium and hafnium-based MOFs, the influence of titanium in the adsorption and reduction mechanism of I2 is highlighted through a change of the Ti4+ cations' oxidation state. As the band gap energy of MOF materials exhibited an effect over the charge transfer complexes involved in the reaction mechanism for different I2@MOF systems, a combination of methodologies was proposed to determine band gap energies and types using only diffuse reflectance UV-Vis data. The study emphasizes how confinement in porous materials can alter properties and stabilization mechanisms, influencing adsorption and reactivity
Hijazi, Amal. "Étude de silices mésoporeuses modifiées pour la capture de l'iode". Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0307.
Texto completoSince the recent nuclear accident in Fukushima (2011), many R&D works were focused on the design of improved dry filters for the capture of radioactive fission products such as volatile iodine species (mainly I2 and CH3I). In this study, a novel class of organic/inorganic hybrid adsorbents with high affinity for iodine was investigated. About 20 different organically-modified silica sorbents with periodic mesoporosity (SBA-15 and PMOs) were prepared using one-pot or two-pot synthesis strategies. These sorbents were characterized by elemental analysis, TGA, N2 porosimetry at 77K, SAXS, DR-UV-Vis, Raman, ATR/IR and DRIFT spectroscopies to establish the relationships between their chemical, structural and textural properties on one hand, and their iodine adsorption behavior on the other hand. Their adsorption capacities and thermal trapping stabilities, were obtained from liquid and gas-phase (breakthrough) experiments carried out at different temperatures (20-100°C). After-test characterization of the spent sorbents was used to shed light on the nature of surface interactions existing between amine species and iodine. The syntheses of different lots of parent SBA-15 material at a scale of ≈ 10 g was found to be rather reproducible with specific surface areas ≈ 700-800 m2/g, porous volume ≈ 0.8-0.9 cm3/g and uniform pore size distribution ca 7-8 nm (from BJH method). The post-incorporation of different types of amines, aminosilanes, or thiols with N (or S) content in the range 2-8 wt% by reflux in toluene at 90oC led to a rather significant decrease of textural characteristics (by 60-80%) and in general an acceptable preservation of the hexagonal SBA-15 structure (SAXS d100= 9.7 nm and a0= 11.2 nm). However, one-pot synthesis strategies (co-condensation and direct synthesis of Periodic Mesoporous Organosilicas (PMOs) led to sorbents with a lower degree of organization, with sometimes very low textural characteristics and probably less accessible –N or –S adsorption sites embedded within the pore walls. Iodine adsorption tests carried out in cyclohexane solvent at 20°C or using breakthrough experiments at 100°C led to rather similar conclusions. The modification with amine- and thiol-containing compounds is essential to enhance the adsorption capacities, especially in the case of I2, while CH3I was about 10 times less easily adsorbed. The most influential material parameter on I2 adsorption capacities is the N (or S) elemental content of the adsorbents, with sometimes quasi-linear relationships existing between both sets of data. On the other hand, other parameters such as the textural characteristics and the type (primary, secondary…) and density of amine groups were found to be less important, except when the surface specific area is very low. SBA-15 adsorbents impregnated with different loadings (19, 38, 51 wt%) of branched polyethyleneimine (PEI) were also investigated for iodine adsorption. Owing to a high density of amine groups and high N content (up to 16.6 wt%), these adsorbents displayed improved characteristics for I2 adsorption, in a way rather similar to what was shown in the literature for CO2 adsorption. For a 38 wt% PEI loading, an exceptionally high I2 adsorption capacity exceeding 2g/g was found for an extended range of adsorption conditions. Above this threshold, the presence of excess PEI led to a total collapse of textural characteristics and a decrease of adsorption capacity. The usable temperature range of these sorbents is however limited to 150-200°C due to limited thermal stability of organic groups. The after-test spectroscopic investigations of different amine-modified SBA-15 sorbents, shows that besides physisorption phenomena, iodine adsorption proceeds via charge-transfer complex formation. Once formed, these CT complexes partially transformed in presence of humidity or silanol groups to ionic species of higher thermal stability
Daouli, Ayoub. "Ab initio exploration of materials for the detection and selective capture of iodine species and nitrogen oxide". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0023.
Texto completoRadioactive isotopes of iodine, such as ¹²⁹I and ¹³¹I, are likely to be disseminated in the environment after a serious nuclear accident or a leak in fuel reprocessing facilities, under the form of highly volatile gaseous species, I₂ and ICH₃, resulting in dramatic consequences. It is therefore necessary to accurately detect these molecules and develop passive filters for trapping them. The challenge today is to find an effective solution that can be applied in nuclear conditions. In particular, the presence of other gaseous species called contaminants, such as CO, H₂O and O₂ can affect the performance of materials used to detect or trap these iodine volatile species in a perennial manner. Molecular scale simulation methods provide a fundamental understanding of the observed phenomena, providing in-depth knowledge at the atomic level that is often difficult to obtain by experimental methods. In this work, density function theory (DFT) calculations and grand canonical Monte Carlo (GCMC) simulations have been used to identify promising materials for the detection and capture of gaseous molecules. Regarding sensing, graphene, and two-dimensional carbon materials (BC₃, C₃N, BCN₆-2) are promising candidates. For graphene, our results reveal that in terms of thermodynamic selectivity, PG (pristine graphene), Cu_PG (copper-doped pristine graphene) and to a lesser extent Ag_MG (silver-doped monolayer graphene) are clearly the most interesting graphene monolayers for the selective capture of I₂, ICH₃ in the presence of CO, H₂O and O₂. As far as 2D carbon materials are concerned, results of adsorption on C₃N seem very promising insofar the difference between the adsorption energies of (I₂, ICH₃) vs (CO, H₂O) is very significant. These findings are strengthened by simulations at finite temperatures. In addition, a discussion of electronic structure calculations is also provided. For trapping, we have selected a class of porous materials named Metal-Organic Frameworks (MOFs). Our systematic evaluation of the adsorption performance of M-MOF-74 where M = Mg, Zn, Cu, Fe, Co, Ni and Mn showed that from a thermodynamic point of view, Fe-MOF-74 and Cu-MOF-74 are clearly the most interesting structures for the selective capture of iodine compounds. A second application addressed in this thesis, still in the context of noxious gases, is the adsorption of NOx emissions. These emissions in a confined work environment without ventilation or treatment represent a major concern. Recent studies have revealed that zeolites can provide effective capture of NOx. In this context, our results reveal that from a series of divalent cations-exchanged zeolite (Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Fe²⁺, Cu²⁺, Zn²⁺, Pd²⁺, Pt²⁺), Faujasite Y-Pt²⁺, is an interesting material for the selective adsorption of NOx from diesel engine exhaust in the presence of water vapor. We then have extended our explorations to MOFs by integrating the same cations as metals into the catecholate ligand prior to its incorporation into the cage-like UiO-66. GCMC simulations implementing a new NOx/MOF force field were deployed to gain an in-depth understanding of the microscopic mechanism involved. Our molecular simulations indicate that the nanoporous UiO-66-CatFe(II) would be an excellent adsorbent for NOx capture, even at very low concentrations of a few ppm. This complements the portfolio of porous materials that, to date, have been almost exclusively tested under operating conditions involving higher NOx concentrations (>1000 ppm)
Bernhard-Bitaud, Corinne. "Modifications de la matière organique et conséquences sur l'adsorption de l'atrazine dans un sol brun de prairie mis en culture". Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL128N.
Texto completoChebbi, Mouheb. "Piégeage d’espèces iodées volatiles sur des adsorbants poreux de type zéolithique dans le contexte d’un accident nucléaire grave". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0340/document.
Texto completoA severe nuclear accident (as Fukushima) may induce dramatic consequences in terms of radiological releases into the environment. The combination of current filtration devices (such as aqueous scrubbers and sand bed filters) with an additional filtration stage made of inorganic porous adsorbent (zeolite) constitute a promising solution in order to avoid the release of radioactive iodine species. The present study aims to establish some correlations between chemical and structural parameters of porous adsorbents mainly silver-zeolites, on the one hand, and adsorption properties towards I2 and CH3I on the other hand. The role played by various zeolitic parameters was assessed by combining adsorption data in gaseous phase (adsorption capacity, decontamination factors, trapping stability) together with physico-chemical data obtained from characterization studies (XRD, ATR/IR, DRIFTS of adsorbed CO, SEM, TEM and DR-UV-Vis). Then, the effect of adsorption temperatures, potential inhibitors and irradiation was also discussed for the most interesting adsorbents in order to extrapolate to severe accidental conditions. The trapping mechanism was also investigated using in-situ spectroscopic accessories as well as theoretical calculations by DFT. It was shown that CH3I adsorption capacities are mainly dependent on the amount of silver that could be deposited in dispersed form (as Ag+, and small clusters) within the internal framework, as well as structural parameters such as pore size. On the other hand, a specific methodology was applied in order to quantify the different forms of stored iodine and therefore to better assess the influence of structural parameters on the trapping thermal stability. It was found that the trapping stability is mainly dependent on silver exchange level and on the nature of zeolitic structure. For the first time, the combination of several spectroscopic techniques was also implemented. On the one hand, in situ Diffuse Reflectance UV-Vis Spectroscopy (DRS-UV-Vis) was employed in order to monitor the evolution of silver species during exposure to gaseous methyl iodide. On the other hand, the time- and temperature-evolution of organic species was investigated using in situ Diffuse Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS) combined with gas-phase reactor measurements. The first step is the dissociation of some CH3I molecules, which is catalyzed by the acidic and silver sites of the zeolite. The dissociated I is then captured by silver to form molecular and clustered AgI entities within the zeolite supercages, which can coalesce and sinter on the external surface upon prolonged exposure to humidity to form silver iodide precipitates (detected by XRD). On the other hand, the carbonaceous part of the CH3I molecules undergo successive catalytic transformations at medium temperatures with zeolite active sites, to yield different by-products (MeOH, DME, higher alkanes, alkenes…). Among all the investigated sorbents for iodine species retention, Ag/Y zeolites have displayed the best retention performances. Promising results were also found in the presence of inhibitors, under irradiation and for low concentrations. The obtained results allow to consider using some of the tested formulations for a nuclear severe accident application, but also to give insights about the behavior of other new adsorbents (Metal Organic Framework MOF and silver-impregnated or functionalized mesoporous silica)