MICROWAVE DRYING OF BOEHMITE SOL INTERCALATED SMECTITES

Monohydroxy aluminium oxide (boehmite) intercalated (cross-linked) smectites (SCLS) have been prepared from an aqueous suspension containing sodium mono-ion-exchanged bentonite (2 wt%) and boehmite (AlOOH) sol at pH 3.5 and at 32-degrees-C. The SCLS has been separated by centrifugation and repeated washing. The intercalated smectite was dried in an oven at 60-degrees-C over a period of 24 h and also in a microwave oven of 2.45 GHz frequency and 600 W power over a range of 3-15 min. Both samples have identical thermal and electrical properties. However, the microwave-dried samples have a distinctly higher surface area of 120 M2 g-1, stable up to 650-degrees-C with a marginal reduction to 116 m2 g-1 compared with 94 M2 g-1 for the oven-dried sample. Similarly there was clear difference in the morphological features of the two samples, the air-dried sample having a close packed structure while the microwave one is delaminated and porous.