Study of the interaction between caesium bromide and kaolinite by differential thermal analysis

Abstract

The reaction occurring during the wet grinding of kaolinite with CsBr was studied by simultaneous Differential Thermal Analysis -Thermogravimetry (DTA-TG), supplemented by infrared spectroscopy of isothermally treated CsBr disks. The DTA and TG curves were compared with those of untreated kaolinite and of kaolinite mixed or air ground with different alkali halides. A new endothermic DTA peak at 75-115 ~ accompanied by weight loss, is due to the desorption of surface and interparticle water located mainly at the "interface" between the mineral and the salt. A second endothermic peak at about 500 ~ represents the simultaneous dehydroJcylation of the clay and thermal hydrolysis of CsBr. The presence of a separate CsBr phase was identified from two endothermic peaks which characterize melting and boiling of the salt; only mixtures with more than 140 mmol CsBr per 100 g kaolinite show the presence of this phase. All of the CsBr below this concentration occurs in the CsBr-HOH-kaolinite intercalation complex. This degree of saturation is smaller than that obtained previously for CsCl.

Organomodified kaolin as a reinforcing filler for natural rubber

“…The DTA profile of unmodified kaolin (EIK) (curve “a”) shows an endotherm in the temperature range 530–560°C, which represents the loss of structural hydroxyls through dehydroxylation producing highly reactive metakaolin. Also, the exotherm peak at around 1001°C is due to the crystallization of the amorphous metakaolinite 72. Both these peaks are visible in the case of an admixture of EIK and SRSO as well as SRSO‐modified kaolin but shifted to lower temperature ranges due to the presence of an impurity phase contributed by the SRSO.…”

Diffuse reflectance infrared spectra of kaolinite and kaolinite/alkali halide mixtures. Curve-fitting of the OH stretching region

“…Therefore, it is plausible that this newly detected band arises from an intercalated water molecule in an environment different from that described previously (l), i.e., one where coordination to both alkali halide ions does not occur. One candidate is the water, possibly located at the interface between kaolinite and the alkali halide, that yields the endothermic DTA peak near 100°C (14). If the band is due to the v, vibration of such a water molecule, then the v, band would fall below 3500 cm-' and contribute to the broad low-frequency wing that extends to the beginning of the OH stretching region.…”

The Effect of Quartz Content on the Mechanochemical Activation of Kaolinite

“…Yariv et al studied the effect of grinding of kaolinite in the presence of alkali halides (18,19, and references therein).…”