Studies on Neptunium ( V ) Carbonate Complexes under Geologic Repository Conditions

THE COMPLEXATION OF NP(V) BY CARBONATE WAS STUDIED AT 0.2 M IONIC STRENGTH USING A SOLVENT EXTRACTION TECHNIQUE WITH A SYNERGIC MIXTURE OF TOMA-TTA IN BENZENE. IN THE INVESTIGATED RANGE OF CARBONATE ALKALINITY (FROM 0 TO 10-2 M) AND PH (8 - 9) THE SPECIES NPO2OH,NPO2(CO3)- AND NPO2(CO3) 2--- WERE IDENTIFIED AND THEIR STABILITY CONSTANTS (BETA) WERE CALCULATED. THE VALUES OF LOG BETA WERE 4.16, 4.13 AND 7.06, RESPECTIVELY. FROM THESE DATA IT APPEARS THAT COMPLEXING BY CARBONATE IS ONE OF THE MAJOR FACTORS AFFECTING THE SPECIATION OF NP(V) IN NATURAL WATERS.NA-NOT AVAILABL