Infrared studies of proton delocalization in kaolinite

Abstract

The delocalization and migration of protons in kaolinite at elevated temperatures have been studied through use of a selective deuteration technique for kaolinite which exchanges OD for lattice OH groups responsible for infrared stretching frequencies at 3695, 3670 and 3650 cm-1 without exchanging the less accessible hydroxy Is with a vibration at 3620 cm-1. Infrared spectra were recorded at room temperature after heat treatment up to 300°C . in both dynamic and static experiments . The degree of redistribution of the protons and deuterons was measured by following the intensity ratio LF (low frequency 3620 cm-1)/HF (high frequency 3695 cm-1) or their OD equivalents. Redistribution of OH and OD is essentially complete in deuterated kaolinite after heating at 300°C for 5 hours. At a temperature of 150°C. redistribution is about 25 percent complete after 54 hours.