Inversion of Montmorillonite Ion-Exchange Characteristics

摘要

The mechanism of montmorillonite modification with sodium metasilicate for inversing its ion-exchange characteristics has been studied. The blockage of the interlayer space in montmorillonite by amorphous silicon-oxygen clusters, which are formed as a result of sodium metasilicate hydrolysis, hinders the access of ions to the internal negatively charged surface of the mineral and increases the strength of bonding between aluminosilicate layers. As a result, adsorption becomes possible only on the outer surface of particles, namely, on active silanol and aluminol groups. This fact has been confirmed by the high rate of the process, as well as by the appearance of the ability to adsorb anions only after the reversal of montmorillonite surface charge. The value of the adsorption of Cr(VI) oxoanions by modified montmorillonite has appeared to be 0.26-1.05 mg/g depending on the synthesis conditions of the samples.