Column-usable inorganic fixator preparation by localized growth on a solid alkaline ferrocyanide

Inorganic fixators are selective sorbents which would often be preferred to commercial ion exchangers if they were suitable for column utilization. We present a new preparation method whose principle is a slow growth of an insoluble compound on a soluble-reacting crystal placed in a concentrated solution of another reactant. By this process, it is possible to prepare mixed zinc or nickel ferrocyanides by local growth on sodium or potassium ferrocyanide crystals placed in a concentrated zinc or nickel solution. The particle size is controlled by the size of the starting solid, the solution concentration and temperature. The growth mechanism seems to be a diffusion of water and divalent ions through the film of insoluble product formed around the soluble crystals. The reaction rate is increased by dilution of the solution or increase of its temperature. This method allows the preparation at low cost of insoluble ferrocyanide columns.