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Rare gas capture and purification is a major challenge for energy, environment, and health applications. Of utmost importance for the nuclear industry, novel separation processes for Xe are urgently needed for spent nuclear fuel reprocessing and nuclear activity monitoring. The recovered, non-radioactive Xe is also of high economic value for lighting, surgical anesthetic, etc. Here, using adsorption and breakthrough experiments and statistical mechanics molecular simulation, we show the outstanding performance of zeolite-supported silver nanoparticles to capture/separate Xe at low concentrations (0.087-100 ppm). We also establish the efficiency of temperature swing adsorption based on such adsorbents for Xe separation from Kr/Xe mixtures and air streams corresponding to off-gases generated by nuclear reprocessing. This study paves the way for the development of novel, cost-efficient technologies relying on the large selectivity/capacity of adsorbent-supported silver nanoparticles which surpass all materials ever tested. [ABSTRACT FROM AUTHOR]

Oversolubility effects refer to a large increase of the solubility of gases in liquids confined in nanoporous solids with respect to the value predicted by Henry's law. This review presents the state of the art of oversolubility by discussing the molecular mechanisms responsible for such effects and the conditions for their observation. Both experimental and theoretical approaches are reviewed, in a non-exhaustive fashion, with special emphasis on results that have helped to unravel the oversolubility phenomenon. Different porous materials including metal-organic frameworks (MOF), ordered porous silicas, and zeolites are considered in combination with various nanoconfined liquids and gases relevant to practical applications in energy and environmental science. Depending on the gas/liquid/solid system considered, oversolubility is shown to pertain either to adsorption (increased concentration at solid/gas and liquid/gas interfaces) or to confinement-induced solubility increase. We also critically discuss when oversolubility effects are expected to lead to improved performance in catalysis or environmental applications such as for air purification. Image 1 • We present the state of the art on oversolubility in nanoporous materials. • Molecular mechanisms are presented and discussed. • Both experimental and theoretical approaches are reviewed with special emphasis on results that have helped unravel the oversolubility phenomenon. • We provide suggestions for future investigations and application perspectives. [ABSTRACT FROM AUTHOR]

Silver nanoparticles are currently one of the most studied nanostructured nanomaterials. Because nanoparticle size and dispersion act together in determining a material's physical and chemical properties, there is a continuous quest to develop size-controlled synthesis methods. Nonetheless, the instability of the nanometer-sized particles, which is caused by their tendency to aggregate irreversibly into larger particles, remains a recurrent problem. The use of confining scaffolds, such as the regular system of cages in a crystalline zeolite-type material, is often reported in the literature as an efficient solution to overcome particle migration at the surface. Silver nanoparticles encapsulated in ZSM-5 (Ag@ZSM-5) represent a new generation of adsorbent for Xe enrichment from the atmosphere that is currently being developed at the pilot scale in a Temperature Swing Adsorption (TSA) process. In this study, we have found that the presence of Cl-containing compounds in the air (VOCs) leads to a poisoning of the active silver phase by the formation of silver chloride. By a careful study of process parameters, we have found that most of the chlorine can be removed by heat treatment above 573 K so that the adsorption properties of silver are regenerated. That said, when applying 573 K temperature regeneration at the pilot scale, we observe a very minor but observable decay of xenon adsorption capacity that continues cycle after cycle. The mechanism of capacity decay is discussed in terms of (i) the residual presence of Cl at the surface of silver nanoparticles, (ii) the aggregation of silver nanoparticles into larger particles (sintering mechanism), and (iii) the acceleration of silver particle migration to the surface and sintering. [ABSTRACT FROM AUTHOR]

Experiment and molecular simulation are used to investigate adsorption in heterogeneous porous media consisting of hierarchical solids (combining different porosity scales) or composite solids (such as silver nanoparticles adsorbed at the external surface of zeolite). It is shown that adsorption in such heterogeneous materials can be written as a linear combination of the adsorption isotherms in its different domains (i.e. porosity scales for the hierarchical sample and constituents for the composite sample). In the case of the composite material, we also show that the linear combination can be used with weighing parameters obtained for a different adsorbate. Such a superimposition principle , which is validated using well-characterized experimental samples, is of interest for characterization purpose as well as industrial applications as they can be used to determine accurately the amount of phases in a given sample (volume corresponding to a given porosity scale or constituent). In contrast, significant departure between the experimental adsorption isotherm and the linear combination can be used to detect coupling effects between the different domains or restrained access to a given domain type. Such a characterization strategy of complex heterogeneous media is complementary to other experiments, such as those probing capillary hysteresis shapes, scanning curves and subloops, which allow determining the distribution of domains within the framework of the independent domain theory. [ABSTRACT FROM AUTHOR]

For the first time, a systematic, consistent domain exploration has been conducted on mono- and bi-cationic exchanged X and Y faujasites for xylene separation using a combinatorial approach. In total, a large, diverse library of 68 faujasites exchanged with alkali cations (Na + , K + , Cs + ) and alkali earth cations (Ca 2+ , Ba 2+ ) was prepared and tested in the presence of three distinct mixture conditions of relevance to the separation process. From the measurements of the 68 × 3 breakthrough curves, we calculated separation performances for the three xylene isomers (p-, m-, o-X), EB, and PDEB. The set of performance properties generated for each adsorbent was analyzed by statistical methods enabling sorting into different classes of selective adsorbents. A rational mapping of exchanged faujasites for xylene separation was performed. [ABSTRACT FROM AUTHOR]