Adsorption of volatile hydrocarbons in iron polysulfide chalcogels

• New quaternary metal chalcogels KFe3Co3S21, KFe3Y3S22 and KFe3Eu3S22 have been synthesized.
• They are predominantly mesoporous materials.
• They show highly selective adsorption for toluene and CO2.
• They have excellent reversible ion-exchange properties.

We report the synthesis, characterization and possible applications of three new metal-chalcogenide aerogels KFe3Co3S21, KFe3Y3S22 and KFe3Eu3S22. Metal acetates react with the alkali metal polychalcogenides in formamide/water mixture to form extended polymeric frameworks that exhibit gelation phenomena. Amorphous aerogels obtained after supercritical CO2 drying have BET surface area from 461 to 573 m2/g. Electron microscopy images and nitrogen adsorption measurements showed that pore sizes are found in micro (below 2 nm), meso (2–50 nm), and macro (above 50 nm) porous regions. These chalcogels possess optical bandgaps in the range of 1.55–2.70 eV. These aerogels have been studied for the adsorption of volatile hydrocarbons and gases. A much higher adsorption of toluene in comparison with cyclohexane and cyclopentane vapors have been observed. The adsorption capacities of the three volatile hydrocarbons are found in the following order: toluene > cyclohexane > cyclopentane. It has been observed that high selectivity in adsorption is feasible with high-surface-area metal chalcogenides. Similarly, almost an eight to ten times increase in adsorption selectivity towards CO2 over H2/CH4 was observed in the aerogels. Moreover, reversible ion-exchange properties for K+/Cs+ ions have also been demonstrated.

Figure optionsDownload as PowerPoint slide