X-ray diffraction study of the effect of microwave treatment of zeolite Na-A

The effect of microwave irradiation on zeolite Na-A has been studied in comparison with classical heat treatment. The thermal behavior and the structural transformations of the zeolite were investigated by X-ray powder diffraction. The structure of zeolite Na-A changed concurrently with microwave treatment. The longer the irradiation period, the larger was the amount of zeolite transformed into another crystalline phase (low-carnegieite), while a decreasing zeolite content remained detectable. On the other hand, during classical heat treatment at 400-800 degreesC, zeolite Na-A went through subsequent structural changes; at about 800 degreesC nepheline (NaAlSiO4) crystallized as a stable phase along with a considerable amount of amorphous material. (C) 2000 Elsevier Science B.V. All rights reserved.