Spectra of partially and fully rehydrated Synthetic Sodium A-Zeolite containing Nickel(II) ions

School of Chemistry, University of Bradford, Bradford, West Yorkshire BD7 1DP, U.K. Manuscript received 23 September 1985, revised 29 May 1986, accepted 23 August 1986 Five samples of synthetic sodium A-zeolite containing 1.0, 2.4, 3.15, 3.9, and 4.6, NiII ions per unit cell were prepared by ion exchange method and characterised. The fully hydrated zeolites showed an octahedral structure of NiII ion. All five samples were dehydrated in vacuum at 620 K and their diffuse reflectance spectra at various stages of rehydration in contact with water vapour recorded. The visual and spectroscopic observations showed the reversible dehydration and rehydration of only Ni1.oA zeolite. After long periods of rehydration, the fully rehydrated samples (greenish) of Ni2.4A, Ni3.15A and Ni3.9A showed band maxima at 23,750 (±50) cm-1. The fully rehydrated sample (yellowish) of Ni4.6A showed band maximum at 2, 500 cm-1. Surface area measurements indicated the structure collapse of only Ni4.6A during evacuation above room temperature. In general, the rate sequence of rehydration of samples investigated, decreases as the Nin ion in the framework increase