Iodine solubility and speciation in glasses

Abstract

The study of iodine in glasses and melts is critical in many areas, from geosciences to materials science to waste management. Glasses in the ternary system Na 2 O-B 2 O 3 -SiO 2 were studied with the goal of identifying a glass matrix able to dissolve large quantities of this element, and to identify the main parameters affecting the solubility of iodine. Two sets of experiments were carried out: the first one with the aim of determining the solubility limit of iodine, and the second one to identify the structural variations occurring within the glass network upon iodine incorporation, and to identify the parameters influencing the most both iodine solubility and speciation. We demonstrated that there is a strong dependence of iodine incorporation on bulk chemistry and glass physical properties. A solubility limit of ~5 mol% I has been assessed for B 2 O 3 -rich glasses and of ~1 mol% for SiO 2 -rich ones, and this composition dependence has been explained by considering the fragility parameter of the glass network. Structural variations in the iodine local environment and in the glass network were characterized by Raman, X-ray Absorption Spectroscopy, and 11 B NMR. Spectroscopy data point out the coexistence of different I species within the glasses, with iodide being the predominant one, surrounded by Na + ions.

The influence of iodide on glass transition temperature of high‐pressure nuclear waste glasses

“…We have shown from Figure 4 that T g is influenced by the presence of I and that increasing I decreases the T g . Comparable behavior has been observed in previous work for B‐rich borosilicate glass compositions 7 . We also show that the influence of I on T g is not the same in between the compositions with a decreasing slope that is more important for ISG than for NH.…”

“…Recent work on B-rich glasses showed that I decreases T g . 7 It appears consistent with the fact that I is considered as a melting accelerator and fining agent. 3,36 However, up to now, investigation of the I effect on T g for borosilicate glass composition relevant to nuclear waste immobilization is not available.…”

“…The effect of iodine on T g is less constrained. Recent work on B‐rich glasses showed that I decreases T g 7 . It appears consistent with the fact that I is considered as a melting accelerator and fining agent 3,36 .…”

“…There has been a growing interest in the incorporation of iodine (I) in glasses in the past few years, especially in the field of Earth sciences 1,2 and in the nuclear waste glasses community. [3][4][5][6][7][8] I has an active radioisotope ( 129 I) that is produced from the nuclear fission of actinides. 9,10 129 I represents a major troublesome element due to its high mobility in the environment, low affinity for claystone, and its long half-life (15.7 My).…”

“…There has been a growing interest in the incorporation of iodine (I) in glasses in the past few years, especially in the field of Earth sciences 1,2 and in the nuclear waste glasses community 3‐8 . I has an active radioisotope ( 129 I) that is produced from the nuclear fission of actinides 9,10 .…”