FT-IR Spectra of Water in Microporous KBr Pellets and Water's Desorption Kinetics

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Abstract
The structure and spectra of water adsorbed on microporous (pore size − ions. This monolayer contains the dominant water in KBr pellets. In the second mode, small water clusters are trapped between the KBr particles and in micropores, and we believe that this type of water is trapped during pellet preparation. Additional water bands, observed at ∼3300 and ∼1670 cm−1, have been assigned to a coordinated type of water, near or at the surface, which constitutes a third type. DSC results indicate that none of the three types of water are capable of forming ice in KBr pellets. On increasing the water content in the pellets, additional water is adsorbed on the top of the monolayer type water, with the other two types being uneffected. The water's desorption kinetics data were tested for ten different decomposition models, and the results can best be described by a 3-dimensional diffusion desorption model, suggesting that micropores are blocked by KBr particles and/or that pores do not run across the width of the pellet.