• journal_title：Clays and Clay Minerals
• Contributor：Wenxing Kuang ; Glenn A. Facey ; Christian Detellier
• Publisher：Clay Minerals Society
• Date：2004-
• Format：text/html
• Language：en
• Identifier：10.1346/CCMN.2004.0520509
• journal_abbrev：Clays and Clay Minerals
• issn：0009-8604
• volume：52
• issue：5
• firstpage：635
• section：Articles

The dehydration and rehydration processes of the clay mineral palygorskite (PFl-1) were studied by textural analysis, thermogravimetric analysis connected with mass spectrometry (TGA-MS), and ²⁹Si and ¹H solid-state NMR techniques. The TGA-MS results clearly reveal weight losses at maxima of 70°C, 190°C, 430°C and 860°C. PFl-1 is characterized by a micropore area of 93 m²/g, corresponding to a micropore volume of 47 mm³/g. These values are also obtained for the sample heated up to 200°C for 20 h. Further heating at 300°C produces a collapse of the structure, as shown by the almost complete loss of microporosity.

The ²⁹Si NMR spectra of palygorskite show two main resonances at −92.0 and −97.5 ppm, attributed to one of the two pairs of equivalent Si nuclei in the basal plane. A minor resonance at −84.3 ppm is attributed to Q²(Si-OH) Si nuclei. The resonance at −92.0 ppm is assigned to the central Si position, while the resonance at −97.5 ppm is assigned to the edge Si sites. It is confirmed by solid-state ²⁹Si and ¹H NMR that nearly complete rehydration is achieved by exposing palygorskite samples that have been partially dehydrated at 150°C and 300°C, to D₂O or water vapor at room temperature. When the rehydration is accomplished with D₂O, the atoms are disordered across all the protons sites.