Adsorption and ion exchange phenomena on synthetic zeolite 4A in alkali nitrates melt

Abstract

The exchange process between the zeolite Linde Molecular Sieve 4A in two cobaltous forms, CoR 2 and CoR 2 nCo(NO 3) 2, and molten lithium-potassium nitrate eutectic mixture has been investigated in the temperature range 160–190°C. It has been found that two types of adsorption sites exist for the exchange process in the melt. These are the ion exchangeable sites, and the adsorption sites resulting from the inclusion of salt in the zeolite cavities. The desorption of cobaltous ions from the CoR 2 form takes place in one step, because only ion exchangeable sites are occupied, while from the CoR 2 nCo(NO 3) 2 form it takes place in two steps, both sites being occupied by cobalt. Diffusion through the solid is the rate determining step.