Expansibility of vermiculites irradiated with microwaves

The effect of microwave power on the expansion of vermiculites was studied at 800 W for different microwave exposure times (from 10 s to 600 s) and compared with the changes after heating to 1000 °C and dehydration in vacuum. The interlayer water molecules of the individual flakes were driven off quickly by microwave irradiation separating the layers. The changes were characterized by X-ray powder diffraction and scanning electron microscopy. Microwave irradiation reduced the time and energy required for the preparation of expanded vermiculite particles. Microwave-heated vermiculites may be useful for some applications, such as intumescent fire barriers. They could also be interesting materials for adsorption of contaminants, such as oil and aromatics compounds (benzene, toluene, chlorobenzene, nitrobenzene, etc.) or heavy metals ions from aqueous solutions, without the need of hydrophobic modification.