SORPTION AND TRANSPORT OF SPECIES IN SILICALITE STUDY OF BINARY-SYSTEMS CONTAINING IODINE

Sorption of iodine from both the vapour phase and iodine solutions in organic solvents on large Silicalite-1 crystals was investigated. The single component sorption of iodine and sorption from binary mixtures under co-diffusion conditions led to a uniform colouring of the crysta ls. Under counter-diffusion conditions with crystals saturated initial ly with vapour of a selected solvent, the sorption kinetics of iodine was 2 or 3 orders of magnitude slower as compared with the correspondi ng co-diffusion experiment. Colouring of crystals was always, at least in its initial stage, non-uniform with visualized pyramids at crystal basal planes. This finding together with the nature of outer and inne r crystal morphology suggests that our Silicalite-1 crystals are 90 de grees-intergrowths which have only pore mouth openings of sinusoidal c hannels in the crystal surface. The process of crystal colouring under counter-diffusion conditions seems to proceed via diffusion along the boundaries of crystal sections.