Interactions between the iron and the aluminum minerals during the heating of Venezuelan lateritic bauxites. I. Infrared spectroscopy investigation

The thermal dehydroxylation of natural Al-bearing geothite was investigated by IR spectroscopy. Venezuelan lateritic bauxites (which in addition to goethite contain kaolinite, gibbsite, ilmenite and quartz), as well as chemically isolated samples of Al-goethites, were heated to 300, 600 and 1000°C. The spectral features of the iron oxides formed during the thermal treatment depend on the heating temperature, showing that the first dehydroxylation product is Al-bearing protohematite which at temperatures above 600°C is recrystallized to Al-bearing hematite. Part of the aluminum which is occuled in this hematite originates from the gibbsite and to a smaller extent from the kaolinite.