Application of Phosphate Precipitation for Removing Strontium and Barium from Alkali Chloride Based Melts

Abstract

The reaction of solutions of barium and strontium chlorides in LiCl–KCl, NaCl–KCl, and NaCl–KCl–CsCl based melts with sodium orthophosphate was studied at 450 and 750oC. The initial phosphate-to-alkaline earth molar ratio varied from 0.5 to 14 and the excess of phosphate required for the complete conversion of AECl2 (AE = Sr, Ba) to phosphates as well as phase composition of the phosphates produced were determined. Normal orthophosphates alongside with lithium phosphate were formed in lithium chloride containing melts, whilst double alkali–alkaline earth phosphates and chloro-phosphates were obtained in NaCl–KCl and NaCl–KCl–CsCl based melts. Size of the particles comprising solid precipitates was determined; the values varied from 0.1 to tens microns. Increasing the initial PO4 3– : AE2+ molar ratio did not have a pronounced effect on the particle size.