Separation of Mercury from Aqueous Mercuric Chloride Solutions by Onion Skins

Abstract

The separation of mercury from aqueous HgCl₂ solutions by onion skins (outermost coat) was studied both experimentally and theoretically. The distribution equilibria were measured by the batchwise method. The experimental results revealed that onion skin is a useful material for separating mercury from aqueous systems. The distribution data obtained at 25°C were analyzed by using the theory based on the law of mass action. The separation of dissolved mercury by onion skins was found to be a process accompanied by an ion-exchange reaction of the cationic complex HgCl⁺ and an adsorption of the neutral complex HgCl₂. The equilibrium constants of the ion-exchange and adsorption processes at 25°C and the mercury-binding capacity of onion skins were determined. Further, it was found that the distribution equilibrium of mercury is comparatively insensitive to temperature.