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CO₂ Sequestration by Bile Salt Aqueous Solutions and Formation of Supramolecular Hydrogels

Zhang, Meng, Ma, Zhiyuan, Wang, Kaojin, Zhu, X. X.
ACS sustainable chemistry & engineering 2019 v.7 no.4 pp. 3949-3955
aqueous solutions, bile salts, carbon dioxide, carbon sequestration, deoxycholic acid, desorption, gelation, hydrogels, mechanical properties, nanofibers, storage modulus
Bubbling carbon dioxide (CO₂) into aqueous solutions of bile salts such as sodium deoxycholate caused a gelation of the solution, forming a hydrogel made of entirely natural biological molecules and providing a convenient storage reservoir of CO₂ in water. The carboxylate group of the bile salt becomes protonated in the aqueous solutions to make the bile acid only marginally soluble in water, which induces the formation of a supramolecular hydrogel with nanofibrous structures. Such hydrogels show convenient gel–sol transition by the desorption of CO₂. The mechanical properties of the hydrogels may be varied by the amounts of CO₂ in the media, reaching a peak value of the storage modulus of the hydrogel. Bubbling CO₂ initially yielded a transparent hydrogel which upon continued purging became mechanically stronger and optically opaque. The bile salt aqueous solutions absorb CO₂ effectively and may potentially serve as an alternative material for CO₂ capture and storage.