Equilibria in uranyl carbonate systems

The equilibrium in solution between the tricarbonate and dicarbonate complexes of the uranyl ion has been investigated. It has been shown that these species are the only species of the uranyl ion existing in solutions of sodium bicarbonate in the concentration range 0.03 M to 0.15 M. It has also been concluded that it is not feasible to isolate the dicarbonate complex as the only form of UO22+ in carbonate media. A spectrophotometric determination of the third formation constant of UO2(CO3)34- gave a value for k3 = 3.01 x 105 (t = 200, μ = 0.1). An extension of the solvent extraction method previously applied to the determination of the overall stability constant of UO2(CO3)22- gave a value of βsub(2(C)) = 1.67 x 1016 (t = 200, μ = 0.1). The absorption spectrum of UO2(CO3)22- has been calculated from equilibrium and optical density measurement. (author)