Removal of Alkaline-Earth Elements by a Carbonate Precipitation in a Chloride Molten Salt

Separation of some alkaline-earth chlorides (Sr, Ba) was investigated by using carbonate injection method in LiCl-KCl eutectic and LiCl molten salts. The effects of the injected molar ratio of carbonate ([K₂ (or Li₂)CO₃/Sr (or Ba)Cl₂]) and the temperature (450–750 °C) on the conversion ratio of the Sr or Ba carbonate were determined. In addition, the form of the Sr and Ba carbonate resulting from the carbonation reaction with carbonates was identified via XRD and SEM-EDS analysis. In these experiments, the carbonate injection method can remove Sr and Ba chlorides effectively over 99% in both LiCl-KCl eutectic and LiCl molten salt conditions. When Sr and Ba were co-presented in the eutectic molten salt, they were carbonated in a form of Ba_0.5Sr_0.3CO₃. And when Sr was present in LiCl molten salt, it was carbonated in the form of SrCO₃. Carbonation ratio increased with a decreasing temperature and it was more favorable in the case of a K₂CO₃ injection than that of Li₂CO₃. Based on this experiment, it is postulated that carbonate precipitation method has the potential for removing alkali-earth chlorides from LiCl-KCl eutectic and LiCl molten salts.