A chalcogel or properly metal chalcogenide aerogel is an aerogel made from

chalcogenide : 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment. A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements ...

s. Chalcogels preferentially absorb heavy metals, such as mercury,

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

, and

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

, from water. Sulfide chalcogels are also very good at

desulfurization Desulfurization or desulphurisation is a chemical process for the removal of sulfur from a material. This involves either the removal of sulfur from a molecule (''e.g.'' A=S → A:) or the removal of sulfur compounds from a mixture such as oil refin ...

. Metal chalcogenide aerogels can be prepared from thiolysis or nanoparticle condensation and contain crystalline nanoparticles in the structure. The synthetic method can be extended to many thioanions, including

tetrathiomolybdate Tetrathiomolybdate, also spelled tiomolibdate (USAN), is the anion of the following salts: * Ammonium tetrathiomolybdate, a building block in bioinorganic chemistry * Bis-choline tetrathiomolybdate Tiomolibdic acid (trade name Decuprate) is a c ...

-based chalcogels. Different metal ions have been used as linkers Co²⁺, Ni²⁺, Pb²⁺, Cd²⁺, Bi³⁺, Cr³⁺. When the gels are dried aerogels with high surface areas are obtained and the materials have multifunctional nature. For example, chalcogels are especially promising for gas separation. They were reported to exhibit high selectivity in CO₂ and C₂H₆ over H₂ and CH₄ adsorption. The latter is relevant to exit gas stream composition of

water gas shift reaction Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a s ...

and steam reforming reactions (reactions widely used for H₂ production). For example, separation of gas pairs such as CO₂/H₂, CO₂/CH₄, and CO₂/N₂ are key steps in precombustion capture of CO₂, natural gas sweetening and postcombustion capture of CO₂ processes leading ultimately at upgrading of the raw gas. The above mentioned conditioning makes the gas suitable for a number of applications in fuel cells. Chalcogels were shown to be very effective at capturing radionuclides from

nuclear waste Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons ...

such as ⁹⁹Tc, and ²³⁸U, and especially ¹²⁹I.

References

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External links

Detailed background about the synthesis and applications of metal chalcogenide aerogels on Aerogel.org
Aerogels Chalcogenides