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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sr(IO3)2 by Materials Project

Sr(IO3)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is two-dimensional and consists of two Sr(IO3)2 sheets oriented in the (0, 0, 1) direction. Sr2+ is bonded to seven O2- atoms to form distorted corner-sharing SrO7 pentagonal bipyramids. There are a spread of Sr–O bond distances ranging from 2.50–2.67 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Sr2+ and one I5+ atom. The O–I bond length is 1.85 Å. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Sr2+ and one I5+ atom. The O–I bond length is 1.84 Å. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Sr2+ and one I5+ atom. The O–I bond length is 1.84 Å. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sr2+ and one I5+ atom. The O–I bond length is 1.85 Å. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Sr2+ and two I5+ atoms. There are one shorter (1.86 Å) and one longer (2.67 Å) O–I bond lengths. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Sr2+ and one I5+ atom. The O–I bond length is 1.84 Å. There are two inequivalent I5+ sites. In the first I5+ site, I5+ is bonded in a 3-coordinate geometry to four O2- atoms. In the second I5+ site, I5+ is bonded in a 3-coordinate geometry to three O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Environmental remediation with functional aerogels and xerogels

Several different types of aerogel and/or xerogel scaffolds have been demonstrated as effective sorbents for the capture and immobilization of radionuclides in gaseous form [e.g., iodine gas or I2(g), Xe] as well as ionic form (e.g., Ce4+, Cs+, I–, IO3-, Rb+, Sr2+, 99Tc7+, and U6+). These scaffolds have unique properties, which include high specific surface areas, high pore volumes, varieties of pore sizes, and functionalities that provide methods for binding radionuclides through physisorption, chemisorption, or a combination thereof. This combination of properties and functionalities make these types of materials ideal scaffolds for use as sorbents for capturing radionuclides. The primary base materials that will be discussed in this chapter include Ag0-functionalized silica aerogels, Ag+-impregnated aluminosilicate aerogels, Ag0-functionalized aluminosilicate aerogels, metal-impregnated (non-Ag) aluminosilicate aerogels and xerogels, sulfide-based aerogels, and carbon-based aerogel composites. For the capture of I2(g), the materials reported herein show some of the highest iodine loadings ever reported for inorganic sorbents. For the capture of ionic species, these materials also show promise to be some of the next generations of materials for active radionuclide remediation. This progress report will describe how these materials are fabricated, the general properties of these materials, as well as an overview of how they have been used for different applications in environmental remediation of radionuclides.

aerogel, xerogel, iodine, radionuclide remediation↗