Emanation thermal analysis of TIXOTON (activated bentonite) treated with organic compounds

TIXOTON (Ca-bentonite activated by sodium carbonate) was treated with four different organic compounds representing organic acids, bases, non-ionic polar molecules and non-polar molecules found in waste and sewage water. They were acetic acid, diethylamine, ethyleneglycol and n-heptane. The first three were used as 5% aqueous solutions, and the latter as a neat liquid. Cation exchange reactions, which occurred between the montmorillonite fraction of TIXOTON and acetic acid or diethylamine solutions, resulted in H-Al-montmorillonite or diethylammonium-montmorillonite, respectively. Ethyleneglycol displaced water in the interlayer space of montmorillonite, and n-heptane was adsorbed on other components of the TIXOTON. The products were characterized by emanation thermal analysis (ETA) supplemented by TG and XRD. The ETA revealed "in situ" microstructure changes of montmorillonite, iron hydrous-oxide and amorphous silica, occuring during the heating of TIXOTON treated with the organic compounds. These changes accompany thermal dehydration, dehydroxylation and formation of meta-montmorillonite, and its subsequent annealing and recrystallization. The organic compounds have an influence on the interlayer water structure and the temperature at which the annealing of the meta-phase begins.