Adsorption properties of iodine on fused silica surfaces when evaporated from tellurium in various atmospheres

Abstract

The evaporation of iodine containing species from tellurium has been investigated together with their adsorption behavior on a fused silica surface. In inert gas, the formation of two species was observed with adsorption enthalpies of around − 90 to − 100 and − 110 to − 120 kJ/mol, respectively. For reducing environments, a single species identified as monatomic iodine was observed with an adsorption enthalpy around − 95 kJ/mol. In oxidizing conditions, species with low adsorption enthalpies ranging from − 65 to − 80 kJ/mol were observed. Presumably, these are iodine oxides as well as oxo-acids of iodine (HIOx). The results of the thermochromatography experiments performed here prove the usefulness of the employed production method for carrier-free iodine isotopes and enhance the understanding of the evaporation and deposition behavior of iodine under various chemical conditions.

Thermochromatographic behavior of iodine in fused silica columns when evaporated from lead–bismuth eutectic

“…Because the tellurium concentration in LBE is rather high and iodine is formed from tellurium distributed in the LBE matrix when irradiating the LBE samples, potential formation of tellurium iodides must be considered when interpreting the results. Indeed, depositions with adsorption enthalpies between − 110 and − 120 kJ mol −1 observed in a recent thermochromatography study on neutron irradiated pure tellurium samples were attributed to tellurium iodides [19]. Thermodynamic data on tellurium iodides are scarce.…”

Radionuclide Chemistry in Nuclear Facilities Based on Heavy Liquid Metal Coolants: Past, Present and Future

“…[44,53] Experiments with caesium-doped LBE indicate that the caesium released from LBE is not adsorbed to steel and fused silica surfaces in thermochromatography experiments but rather reacts with these surfaces at temperatures between 400 and 700 °C, leading to a fixation of the volatile species. [44,54] Similar studies performed for polonium revealed that polonium, when it is evaporated in elemental form from samples that do not contain elements of the LBE matrix, adsorbs to steel slightly more strongly than to fused silica surfaces. More importantly, the formation of volatile species observed in similar experiments in fused silica columns with moist inert and reducing carrier gases was not observed in steel columns, indicating that the steel used as construction material for MYRRHA can suppress the formation of these species.…”

“…Thermochromatography studies on iodine evaporated from LBE indicate that in helium and hydrogen gas bismuth monoiodide is formed and deposited at relatively low temperatures (100-180 °C). [44,52] In oxidising atmosphere, even more volatile species such as monatomic iodine and iodine oxides are formed. However, the adsorption of iodine evaporated from LBE Fig.…”