Separation of Mercury from Aqueous Mercuric Chloride Solutions by Onion Skins

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Abstract
The separation of mercury from aqeous 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.degree.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.degree.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.