Isotopic effect on the hydration-dehydration studies of βbc-nickel hydroxide using infrared spectroscopy

Abstract

β and βbc-nickel hydroxides are the two polymorphs obtained by simple precipitation method. βbc-nickel hydroxide contains water of hydration bonded to the layers of [Ni(OH)6] octahedron by chemisorption process. OH¯ due to [Ni(OH)6] octahedron from the layer and water of hydration is of two types of OH¯ groups present in the bc-nickel hydroxide sample. The water of hydration is reversible in nature and can be dehydrated and hydrated at about 125oC and is treated as reversible moisture content. Using IR spectroscopic technique, the two types of hydroxyl stretching vibrational frequencies can be easily identified. In this study, isotopic exchange (D2O) of reversible moisture content (H2O) in βbc-nickel hydroxide has been carried out. βbc-nickel hydroxide sample was heated to about 1250C and on exposure to deuterium water vapours for overnight results in the changes in the vibrational bands of the infrared spectrum. βbc-nickel hydroxide saturated with deuterated water was re-heated to eliminate it and re-equilibrated in saturated water (H2O) vapour. Variation in the relative intensities, appearance and disappearance of bands in the IR spectra during the heating and cooling process was monitored.