Raman Spectroscopy of Adsorbed Water in Clays: First Attempt at Band Assignment

Raman spectroscopy can be a useful tool to determine water content within clays, or even in highly saturated solutions. The following assignment is proposed for the OH region of SAz-2: the two large bands at 3260 and 3475 cm-1 are assigned to water in pores, the first one to water molecules coordinated to the interlayer cations, and the second one to structural Al-OH groups The band at 3600 cm-1 is therefore more likely related to adsorbed water on the clay surface. Simple intensity ratios of these different bands give good estimates of water content.