Published: Apr 2002
Pages: 93 - 98
Authors: JANA HROBARIKOVA, PETER KOMADEL
Abstract: Four series of reduced-charge montmorillonites, with ranges in layer charge, were prepared from parent Ca-montmorillonites of various chemical compositions. Fine fractions of bentonites from Otay (USA), Ivancice (Czech Republic), Sarigus (Armenia) and Kriva Palanka (Macedonia) were used. The extent of ion exchange, 62–89 % of CEC covered by Li+, was dependent on the mineral and on the Li+, concentration in the liquid phase. Different levels of charge reduction were achieved via Li-fixation by heating the samples for 24 h at 110–300 °C. Li+, ions were fixed in the layers of all four montmorillonites, but incomplete Li+, for Ca2+ exchange diminished the extent of charge reduction. Heating the samples at temperatures up to 140 °C caused Li-fixation and reduction in relative cation-exchange capacity (CEC) values by 32 to 48 % but only a decrease by 17 to 24 % in the sorption of water and by 4 to 14 % of ethylene glycol monoethyl ether. The greatest changes in these properties were observed among the samples prepared at 130–200 °C, while higher temperatures had little effect. The most extensive reduction in CEC, by 81 % after preparation at 300 °C, was obtained for the Otay montmorillonite, the mineral with the highest octahedral and the lowest tetrahedral charge and the greatest level of Li+, for Ca2+ exchange. Higher tetrahedral charge and a lower level of Li+, for Ca2+ exchange negatively affected the decrease in the cation exchange capacities, the specific surface areas and the water uptake capabilities of the prepared reduced-charge montmorillonites.
Keywords: water sorption, EGME specific surface area, cation-exchange capacity, Li-fixation, montmo-rilloniteDownload PDF document