Dissolution behavior of silicalite crystal

The dissolution behavior of the three faces of a silicalite crystal in a NaOH solution at high temperatures of hydrothermal condition was studied by interferometry, which directly provided the dissolution rate along the crystal depth. It was found that the dissolution of the (010) face starts from the crystal edge and that the slope of the crystal remains constant. An optically visible etch pit was hardly observed for crystals without hillocks and not exhibiting intergrowth. The apparent activation energy of the dissolution of each crystal face was comparable to that of a quartz crystal. The leaching process of silicalite crystals in an HF solution proceeded at room temperature and also started from the crystal edge. It was concluded that the dissolution method using a base or an acid solution is suitable for the characterization of zeolite crystals. (C) Elsevier Science Inc. 1997.