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Acidity of Alginate Aerogels Studied by FTIR Spectroscopy of Probe Molecules |
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| Authors: | Romain Valentin Raluca Horga Barbara Bonelli Edoardo Garrone Francesco Di Renzo Françoise Quignard |
| Affiliation: | 1. Laboratoire de Matériaux Catalytiques et Catalyse en Chimie Organique, UMR 5618 CNRS-ENSCM-UM1, Institut C. Gerhardt, FR 1878, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 5, France;2. Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino, C.so Duca degli Abruzzi 24, I-10129 Torino, Italy |
| Abstract: | Supercritical drying of alginate gels is an efficient way to prepare aerogels with high surface area (>300 m2 · g−1). FTIR spectroscopy allows to monitor the adsorption of NH3 from the gas phase onto the acid sites of the alginate. Free carboxylic groups are effective Brønsted sites, whereas the divalent cations used in the ionotropic gelation present the properties of Lewis sites. The ratio between Brønsted and Lewis sites provides infomation on the role of pH in alginate gelation and suggests that non-buffered gelation by transition-metal cations is a mixed ionotropic-acid process. |
| Keywords: | aerogel alginate ammonia adsorption FTIR spectroscopy supercritical drying |