Approach to a descriptive model of charge reduction in vermiculite by hydrothermal treatment

Vermiculites have the potential to serve as effective catalysts if pillared with Al, but their high charge presents an obstacle to the pillaring process. The purpose of this studywas to submit natural vermiculite to thermal treatments in the presence of water vapor in order to effect a reduction in the global negative charge and therebyto enhance its susceptibilityto pillaring. The process of charge reduction in vermiculite under the conditions selected involved the extraction of 25% of Al accompanied bythe extraction of structural Mg and charge-compensating cations (Ca, Na, and K). The results indicate a reduction of 35% in the global negative charge in vermiculite bythe end of the treatment. Some of the Al content was not removed during acid washing, and probablyremained in the solid in structural positions in the octahedral sheet