USE OF ALKALINE-EARTH AND MAGNESIUM CARBONATES FOR PURIFICATION OF SODIUM-CHLORIDE AND KCL SOLUTIONS FROM RARE-EARTH ELEMENTS OF THE CERIUM SUBGROUP

Sorption of ionic forms of Ln3+ elements of the cerium subgroup (where Ln3+ = La3+, Ce3+, Pr3+, Nd3+, and Sm3+) on carbonates of alkaline earths (AE) and magnesium from water over a wide range of sodium- (0.6-4.4 M) and potassium chloride concentrations was studied. The chlorides were used as supporting electrolytes at pH = 7-8 and a working temperature of (298 +/- 0.1) K. The sorptive properties of MgCO3.3H2O, CaCO3, SrCO3, and BaCO3 powders were studied systematically. Their principal sorptive characteristics relative to the indicated rare earth elements (REE) were obtained. In particular, the degree of extraction F, the statistical exchange volume (SEV), the sorption values a, and the distribution coefficients K(d) of Ln3+ between the sorbent matrix and the supporting electrolyte were considered as functions of the initial process parameters. The feasibility of the studied AE and magnesium carbonates as sorbents for purification of natural waters from radionuclides Ba-140-La-140, Ce-141, and Ce-144-Pr-144 was checked. The water contained a complex mixture (29-33 days old) of radioactive contaminants from an atomic energy reactor with a total activity of 1.86.10(-7) Ci/liter.