The carbonate complexation of the Am(III) ion

Am(III) carbonate complexation has been investigated in 0.1 M NaClO4 (or 0.3 M NaClO4) under Ar+1% CO2 atmosphere at pH=6.0-9.2. Under these conditions the Am3+ ion precipitated is found to be Am2(CO3)3(s). Solubility and spectroscopic experiments are carried out in parallel. The contribution of hydrolysis reactions to total reactions is found to be small at PCO2=10-2 but considerable at PCO2=10-3.5. The probability of formation of hydroxocarbonate species of Am(III) is discussed. The average constants determined by the two separate experiments are: Log Ksp (Am2(CO3)3)=-29.80±0.10, logβ1=6.22±0.08 and logβ2=9.76±0.17. (orig.)