Page 527 - Handbook of Thermal Analysis of Construction Materials

498 Chapter 12 - Clay-Based Construction Products

Thermograms of kaolinite, illite, nontronite, and montmorillonite
with three basic dyestuffs, namely, malachite green, methylene blue, and
methyl violet have been investigated. Thermograms of some of the clay
minerals treated with dyes are shown in Fig. 4. [15] All the complexes exhibit
low temperature endothermic peaks smaller than those of the untreated
samples. The organic matter probably occupies the spaces normally held by
the water molecules. Kaolinite-dye complexes show a small exothermal
effect between 350 and 435°C due to the oxidation of the dye adsorbed by
base exchange reaction. Malachite green-kaolinite complex has a much
more intense exotherm than others. Illite-dye complexes (Fig. 4a) indicate
two intense exothermic effects between 200 and 500°C. Nontronite and
montmorillonite dye complexes (Fig. 4b) show three exothermic peaks,
two having pronounced intensities. The second peak in illite complexes at
460–470°C is less intense than that of nontronite-complexes occurring at
600°C. Illites can be differentiated from nontronites by the second
exothermic peak. In montmorillonite complexes, the higher temperature
exothermic peak at 650–670°C serves to differentiate montmorillonites
from nontronites and illites in which it occurs at 600 and 460–470°C,
respectively.

Figure 4. Thermograms of illite and nontronite-dye complexes. (a) Thermograms of illite
and its complexes: (1) illite; (2) malachite green complex; (3) methylene blue complex; (4)
methy violet complex; (5) piperidine complex. (b) Thermograns of nontronite and its
complexes: (1) nontronite; (2) methylene blue complex; (3) malachite green complex; (4)
methyl violet complex; (5) piperidine complex. [15]