PREPARATION AND INFRARED SPECTROSCOPIC CHARACTERIZATION OF REDUCED-CHARGE MONTMORILLONITE WITH VARIOUS LI CONTENTS

A series of reduced-charge montmorillonites (RCMs) was prepared from L i-montmorillonite from Jelsovy Potok (Slovakia) by heating at various temperatures (105-210 degrees C) for 24 h. The amount of fixed Li, 0.0 9-0.67 per O-20(OH)(4), increased with increasing temperature, confirm ing preparation of a set of samples of variable layer charge from the same parent Li-montmorillonite by varying only the preparation tempera ture. Infrared spectroscopy revealed that Li was trapped in the hexago nal cavities of the tetrahedral sheet at all temperatures. Partial dep rotonation of the samples, reflected in the decrease of the intensitie s of the OH-bending bands, was observed after treatments above 120 deg rees C. Analysis of the OH-stretching region showed Li in the previous ly vacant octahedra in the samples heated above 150 degrees C. Weak in flections near 660 and 720 cm-L confirmed development of local triocta hedral character of octahedral cations coordinated with OH groups in t he sample heated at 210 degrees C. Gradual decrease of the layer charg e, due to Li fixation led to a shift of the Si-O stretching band to hi gher frequencies and to the appearance of new, pyrophyllite-like bands at 1120 and 419 cm(-1).