title: Impact of the Si/Al ratio on the selective capture of iodine compounds in silver-mordenite: a periodic DFT study.
abstract: Silver modified zeolites with a mordenite structure can capture volatile iodine compounds (I2and ICH3) which can be released during a severe nuclear accident. However under these particular conditions, molecules such as CO and H2O present in the containment atmosphere are expected to inhibit the adsorption of iodine compounds. In the present work, periodic density functional theory calculations have been carried out to investigate the interaction of I2, ICH3, H2O and CO molecules in silver-exchanged mordenite with various Si/Al ratios with the aim of finding values that favor a selective adsorption of I2and ICH3. Computational results show that the interaction energies of CO and H2O remain of the same order of magnitude (from -120 to -140 kJ mol-1for CO and from -90 to -120 kJ mol-1for H2O) for all the investigated Si/Al ratios. In contrast, ICH3is increasingly strongly adsorbed as the Si/Al ratio decreases, from around -145 kJ mol-1when Si/Al = 47 to -190 kJ mol-1for Si/Al = 5. The same trend is observed for I2with a larger amplitude: from -135 kJ mol-1for Si/Al = 47 to -300 kJ mol-1for Si/Al = 5. Therefore, the use of silver-exchanged mordenite with Si/Al ratios of 5 or 11 would drastically limit the inhibiting effect of contaminants on the adsorption of volatile iodine species. Also for the same ratios, a spontaneous dissociation of I2during its adsorption is observed, leading to the formation of AgI complexes which are prerequisite for the immobilization of iodine in the long term.
authors.affiliation: Laboratoire de Chimie et Physique - Approche Multi échelle des Milieux Complexe (LCP-A2MC, EA 4632), Institut Jean-Barriol FR2843 CNRS, Université de Lorraine, Rue Victor Demange, 57500 Saint-Avold, France. siwar.chibani@univ-lorraine.fr michael.badawi@univ-lorraine.fr.
authors.forename: Siwar
authors.initials: S
authors.lastname: Chibani
authors.affiliation: Laboratoire de Chimie et Physique - Approche Multi échelle des Milieux Complexe (LCP-A2MC, EA 4632), Institut Jean-Barriol FR2843 CNRS, Université de Lorraine, Rue Victor Demange, 57500 Saint-Avold, France. siwar.chibani@univ-lorraine.fr michael.badawi@univ-lorraine.fr.
authors.forename: Mouheb
authors.initials: M
authors.lastname: Chebbi
authors.affiliation: Laboratoire de Cristallographie, Résonance Magnétique et Modélisations (CRM2, UMR CNRS 7036) Institut Jean Barriol, Université de Lorraine, BP 239, Boulevard des Aiguillettes 54506 Vandoeuvre-lès-Nancy, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Lebègue
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire, CE Cadarache, F-13115 Saint Paul lez Durance, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Cantrel
authors.affiliation: Laboratoire de Chimie et Physique - Approche Multi échelle des Milieux Complexe (LCP-A2MC, EA 4632), Institut Jean-Barriol FR2843 CNRS, Université de Lorraine, Rue Victor Demange, 57500 Saint-Avold, France. siwar.chibani@univ-lorraine.fr michael.badawi@univ-lorraine.fr.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-3504-4180
authors.initials: M
authors.lastname: Badawi