A combined synchrotron powder diffraction and vibrational study of the thermal treatment of palygorskite-indigo to produce Maya blue

Manuel Sánchez Del Río, Enrico Boccaleri, Marco Milanesio, Gianluca Croce, Wouter Van Beek, Constantinos Tsiantos, Georgios D. Chyssikos, Vassilis Gionis, George H. Kacandes, Mercedes Suárez, Emilia García-Romero

Risultato della ricerca: Contributo su rivistaArticolo in rivistapeer review

Abstract

The heating process (30-200 °C) of a palygorskite-indigo mixture has been monitored in situ and simultaneously by synchrotron powder diffraction and Raman spectroscopy. During this process, the dye and the clay interact to form Maya blue (MB), a pigment highly resistant to degradation. It is shown that the formation of a very stable pigment occurs in the 70-130 °C interval; i.e., when palygorskite starts to loose zeolitic water, and is accompanied by a reduction of the crystallographic a parameter, as well as by alterations in the C=C and C=O bonds of indigo. Mid- and near-infrared spectroscopic work and microporosity measurements, employed to study the rehydration process after the complex formation, provide evidence for the inhibition of the rehydration of MB as compared with palygorskite. These results are consistent with the blocking of the palygorskite tunnel entrance by indigo molecules with a possible partial penetration inside the tunnels. The surface silanols of palygorskite are not perturbed by indigo, suggesting that MB is not a surface complex.

Lingua originaleInglese
pagine (da-a)5524-5536
Numero di pagine13
RivistaJournal of Materials Science
Volume44
Numero di pubblicazione20
DOI
Stato di pubblicazionePubblicato - ott 2009

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