synthesized an electrode with Congo red containing aniline-SiO 2 xerogels and used these in sensor applications for ascorbic acid. showed that ZrO 2–SiO 2 xerogels adsorb Cr(VI) and can be used as a potentiometric sensor. synthesized a silica xerogel thin film with a low dielectric constant and a high-temperature limit that can be used as an intermetallic dielectric in microelectronics. synthesized Pt-containing carbon xerogels using electrostatic adsorption and demonstrated these to be catalysts for active hydrogenation of benzene into cyclohexane. synthesized Pd–SiO 2, Ag–SiO 2, and Cu–SiO 2 xerogel catalysts with hierarchic textures and concluded that benzene oxidation over Ag–SiO 2 and Cu–SiO 2 xerogels and hydrodechlorination over Pd–SiO 2 xerogels are structure-insensitive reactions. Studies on the applications of xerogels are mostly related to their use as catalysts or sensors. Alternatively, xerogels can be scaled up to various shapes and sizes with much less effort.Ĭatalysis, cosmic dust capture, thermal insulationĬatalysis, energy storage, electrode, sensor, sorbent (9,10,13,14) One limitation to making large quantities and sizes of aerogels using the CPD process is that an adequately sized pressure vessel (i.e., autoclave) is required to hold the sample. (16) In contrast to xerogels, aerogels are often synthesized using critical point drying (CPD, alternatively called supercritical drying), by which the solvent matrix is exchanged with another liquid (e.g., CO 2) that is then taken to a supercritical state by increasing the pressure and temperature of the fluid and vented as a gas to preserve the structure of the initial alcogel. Collapse of the gel pore structure during drying can also be minimized by exchanging the solvent matrix to a nonpolar solvent (e.g., hexane) prior to the drying step. (1,4,5) Xerogels are generally synthesized through slow evaporation of the matrix solvent in the gel at a relatively low temperature (<40 ☌) or at room temperature under vacuum, resulting in volume shrinkage and pore collapse by capillary forces on the pore walls. (9,10,13,14) Both aerogels and xerogels are typically brought to the same alcogel stage (i.e., a solidified gel in an alcohol matrix) under identical preparation processes, but their drying processes vary. (9−15) Compared to aerogels, xerogels generally have smaller SSA, smaller porosities, smaller s p, and larger apparent densities due to differences in the synthesis routes. (1−8) Aerogels and xerogels are porous solids characterized by large specific surface areas (SSAs), high porosities, various pore sizes ( s p), small apparent densities, small indices of refraction, and low thermal conductivities. These results show that Ag-HTX is a promising sorbent for I 2(g) capture with good iodine loading capacity and mechanical stability.Īerogels and xerogels of various compositions have been demonstrated as effective sorbents for the capture of iodine gas. The heat-treatment process increased Young’s modulus (compressive) value to 40.8 MPa from 7.0 MPa of as-made xerogel, demonstrating the need for this added step in the sample preparation process. The hardness of the Na-HTX was >145 times higher than that of the heat-treated aerogel of the same starting composition. The specific surface area of Ag-HTX was 202 m 2 g –1 and decreased to 87 m 2 g –1 after iodine loading. Iodine loading of this xerogel was 0.43 g g –1 at 150 ☌ over 1 day and 0.52 g g –1 at 22 ☌ over 33 days. After I 2(g) capture, the AgI crystallites were observed in the sorbent, verifying chemisorption as the primary iodine capture mechanism. The structural and chemical analyses of Ag-HTX showed uniform distribution of Ag throughout the gel network after Ag-exchange. Samples were characterized by powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis, gravimetric iodine loading, nanoindentation, and dynamic mechanical analysis. After synthesis of the base NaAlSiO 4 xerogel, a heat-treatment step was performed to help increase the mechanical integrity of the NaAlSiO 4 gels (Na-HTX) prior to Ag-exchanging to create Ag-HTX xerogels.

In this work, silver-loaded heat-treated aluminosilicate xerogels (Ag-HTX) were evaluated as sorbents for iodine capture. These isotopes are of particular concern to the environment and human health as they are environmentally mobile and can cause thyroid cancer. Various radionuclides are released as gases during reprocessing of used nuclear fuel or during nuclear accidents including iodine-129 ( 129I) and iodine-131 ( 131I).

Cosmic silverback strain