A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite

作者：Gatta G Diego^*; Rotiroti Nicola; Bersani Danilo; Bellatreccia Fabio; Della Ventura Giancarlo; Rizzato Silvia

来源：Mineralogical Magazine, 2015, 79(7): 1755-1767.

DOI：10.1180/minmag.2015.079.7.03

• merlinoite
• zeolite
• single-crystal X-ray diffraction
• Raman spectroscopy
• IR spectroscopy

A multi-methodological study of the (K,Ca)-variety of the zeolite merlinoite from Fosso Attici, Sacrofano, Italy was carried out on the basis of electron microprobe analysis in wavelength dispersive mode, single-crystal X-ray diffraction (at 100 K), Raman and infrared spectroscopy. The chemical formula of the merlinoite from Fosso Attici is (Na0.37K5.69)(Sigma=6.06)(Mg0.01Ca1.93Ba0.40)(Sigma=2.34)(Fe0.023+Al10.55Si21.38)(Sigma=31.9)O-64 center dot 19.6H(2)O, compatible with the ideal chemical formula K6Ca2[Al10Si22O64]center dot 20H(2)O.
Anisotropic structure refinements confirmed the symmetry and the framework model previously reported (space group Immm, a = 14.066(5), b = 14.111(5), c = 9.943(3) angstrom at 100 K). Refinement converged with four cationic sites and six H2O sites; refined bond distances of the framework tetrahedra suggest a highly disordered Si/Al-distribution. The Raman spectrum of merlinoite (collected between 100 and 4000 cm(-1)) is dominated by a doublet of bands between 496-422 cm(-1), assigned to tetrahedral T-O-T symmetric bending modes. T-O-T antisymmetric stretching is also observed; stretching and bending modes of the H2O molecules are only clearly visible when using a blue laser. The single-crystal near-infrared spectrum shows a very weak band at 6823 cm(-1), assigned to the first overtone of the O-H stretching mode, and a band at 5209 cm(-1), due to the combination of H2O stretching and bending modes. A very broad and convoluted absorption, extending from 3700 to 3000 cm(-1) occurs in the H2O stretching region, while the nu(2) bending mode of H2O is found at 1649 cm(-1). The powder mid-infrared spectrum of merlinoite between 400-1300 cm(-1) is dominated by tetrahedral T-O-T symmetric and antisymmetric stretches. Raman and Fourier-transform infrared spectroscopy spectra of merlinoite and phillipsite provide a quick identification tool for these zeolites, which are often confused due to their close similarity.

• 出版日期2015-12