JOURNAL of the Tunisian Chemical Society

The activation effect generated by the dry grinding of a commercial quartz-free kaolin and a natural Tunisian quartz-rich kaolin was studied. The Tunisian kaolin has a similar chemical composition to that of pyrophyllite. The grinding operation was conducted using a laboratory planetary ball mill, while adding triethanolamine as a grinding aid. The textural analyses show that the grinding does not seem to follow the three steps conventionally observed when minerals are ground without the use of a grinding aid. The latter seems to prevent the particles agglomeration when minerals are milled for a long time. Regardless of the presence of quartz, a rapid and significant alteration of the kaolinite structure during the first 30 min of grinding was observed. Beyond those 30 min, alteration attenuates clearly. The distortion of the quartz structure follows a different evolution. Thermal events show classical evolution of the kaolinite dehydroxylation peak. However, the presence of quartz seems to affect the mullite crystallization peak: for the quartz-free sample, this peak widens but for the quartz-rich sample, it refines and its intensity increases when prolonging grinding. It is likely that Si-O-Al bonds are formed during grinding, where Si is derived from quartz and Al from kaolinite.

N. Ben Messaoud, Z. Ksibi, L. Bergaoui

Kaolinite, quartz, grinding, grinding aid, mullite

Pages: 264-275