Complexation of U(VI), Ce(III) and Nd(III) with acetohydroxamic acid in perchlorate aqueous solution

Complexes of UO22+, Ce3+ and Nd3+ (M) with acetohydroxamic acid (AHA or L) in an aqueous solution have been investigated by the pH-spectral titration method at 25 °C in an aqueous medium of 1.0 M NaClO4 ionic strength. Cerium(III) and neodymium(III) form [ML]2+, [ML2]+, [ML3] complexes with acetohydroxamic acid, while in case of UO22+ form [UO2L]+, [UO2L2] complexes with acetohydroxamic acid. Data processing with SQUAD program calculates the best values for the stability constants from pH-spectrophotometric titration data. The protonation constant obtained was pK1 = 9.15 ± 0.04 at 25 °C. The stability constants for acetohydroxamic acid with UO22+, Ce3+ and Nd3+ were β1 = 7.22 ± 0.011, β2 = 14.89 ± 0.018 for UO22+ and β1 = 5.05 ± 0.062, β2 = 10.60 ± 0.076, β3 = 16.23 ± 0.088 for Ce3+ and β1 = 5.90 ± 0.028, β2 = 12.22 ± 0.038, β3 = 18.58 ± 0.042 for Nd3+, respectively.