Iodine Capture with Metal-Functionalized Polyacrylonitrile Composite Beads Containing Ag⁰, Bi⁰, Cu⁰, or Sn⁰ Particles

Abstract

The capture of radioiodine from nuclear processes and the mitigation of environmental release are important topic areas of research. Some of the more commonly employed chemisorption-type iodine scavengers reported in the literature are based on metal-exchanged porous sorbents such as Ag-zeolites or metal-functionalized aerogels and xerogels. However, another option is to use zero-valent metals directly that have known high affinities for iodine gas [i.e., I2(g)]. In this study, fine metal particles of Ag0, Bi0, Cu0, and Sn0 were embedded in porous polyacrylonitrile (PAN) substrates at 75 mass% metal loadings within the form of ellipsoidal beads with maximum diameters of ∼2–3 mm. These composite beads showed extremely high iodine loadings that are directly related to the metal particle loadings. The X-ray diffraction (XRD) analyses of Ag0, Bi0, Cu0, and Sn0 particles as well as metal-PAN composite beads reacted with iodine gas at 120 ± 1 °C showed phases of AgI, BiI3, CuI, and SnI4, respectively. For the Ag-PAN, Cu-PAN, and Sn-PAN beads, no other crystalline peaks were observed in XRD for unreacted metal or oxidized metals after 48 h in saturated I2(g) at 120 ± 1 °C, whereas unreacted metallic Bi0 was observed within the Bi-PAN composites. However, after a 72 h exposure at 120 ± 1 °C, both the Bi0 particles and the Bi-PAN composites showed full conversion from Bi0 to BiI3 with XRD. Comparisons between mass uptake data and X-ray absorption spectroscopy were used to better understand the phase distribution of the Bi phases present in the Bi-PAN+I composites. The iodine loadings (mg iodine per g sorbent, or q e) for these materials were 1120 (Ag-Particle), 1382 (Bi-Particle-72h), 1033 (Cu-Particle), 3000 (Sn-Particle), 753 (Ag-PAN), 1012 (Bi-PAN-72h), 1457 (Cu-PAN), and 1669 (Sn-PAN). It is possible that inexpensive sorbents such as these could be deployed to help limit or prevent release of radioiodine to the environment.

Iodine Capture by Ag-Loaded Solid Sorbents Followed by Ag Recycling and Iodine Immobilization: An End-to-End Process

“…The iodine loading of AgX is m % I = 25% compared to AgZ with m % I ≈ 11%, and this result is roughly in agreement with the ratio of Ag in the initial sorbents. The iodine loading experiments from the current study and previous studies ,,, show that sorbents with higher Ag loading tend to exhibit higher iodine loadings, but this is all dependent on the Ag utilization, which can vary from sorbent to sorbent. In the context of maximizing the iodine loading, maximizing the ion exchange potential for Ag recycle and iodide elution using the process described herein, as well as the chemical and mechanical integrity of the passive scaffold (aluminosilicate frameworks in the case for zeolites), optimization of these parameters in a search for more efficient sorbents should be considered in future studies.…”

Synthesis of and iodine capture with MSx (Ag2S, Bi2S3, Cu2S)–polyacrylonitrile composites

“…In this study, several MS x -PAN composites were produced using a previously reported process 3,7,17,18 where MS x = Ag 2 S (75, 80, or 90 mass%), Bi 2 S 3 (80 mass%), or Cu 2 S (80 mass%). For each batch of composite beads, the general process was the same and all were prepared separately in glass beakers.…”

Hollow Core–Shell Bismuth Based Al‐Doped Silica Materials for Powerful Co‐Sequestration of Radioactive I2 and CH3I

“…After conversion to Bi@Al/SiO 2(4 mL) -2, its PXRD curve corresponds to the PDF card of Bi 0 , indicating the successful transformation from Bi 2 O 3 to Bi 0 . [40][41][42] In addition, no other phase is found, suggesting the amorphous composition of the Al-doped silica shell. In order to compare the role of aluminum in the iodine sorption process, all silicon sample named Bi@Al/SiO 2(4 mL) -∞ was prepared, and its PXRD pattern showed the same characteristics.…”