The study of complex equilibria of uranium(VI) with selenate

Uranyl (M)-selenate (L) complex equilibria in solution were investigated by spectrophotometry in visible range and potentiometry by means of uranyl ion selective electrode. The formation ML and ML2 species was proved and the corresponding stability constants calculated were: log beta(1) = 1.57(6) +/- 0.01(6), log beta(2) = 2.42(3) +/- 0.01(3) (I = 3.0 mol l(-1) Na(ClO4, SeO4) (spectrophotometry) at 298.2 K. Using potentiometry the values for infinite dilution (I --> 0 mol l(-1)) were: log beta(1) = 2.64 +/- 0.01, log beta(2) less than or equal to 3.4 at 298.2 K. Absorption spectra of the complexes were calculated and analysed by deconvolution technique. Derivative spectrophotometry for the chemical model determination has also been successfully applied. (C) 1997 Elsevier Science B.V.