Determination of the compositions of oxalate complexes of uranium(VI) and aluminum(III) by ion flotation

Ion flotation of fourteen metals in oxalate solutions over the pH range of 0.5 -- 6.7 with cationic surfactant, cetylpyridinium chloride (CPC), was investigated. From 12.00 ml of 0.1 M oxalate solution containing metal ion of 5.0 x 10-4M and CPC of 3.3 x 10-3M, uranium(VI) and aluminum(III) were removed completely at pH values > 3.5 and > 5.0, respectively, and 90% of zirconium(IV) at pH 1.0 or more, 95% of antimony(III) at pH 4.7, 78% of gallium(III) at pH 3.5 or more and 68% of indium(III) at pH 3.5 were removed by bubbling nitrogen through a 2.7 (dia) x 20 cm cell for 20 to 30 min. The reaction between oxalatouranate(VI) ions and the surfactant can be considered as follows: 2(anti n - 1)R+Cl- + UO2(C2O4)sub(n)sup(-2(anti n - 1)-) reversible R sub(2(anti n - 1))[UO2(C2O4)sub(anti n) + 2(anti n - 1)Cl- where R+ denotes the surfactant cation and anti n represents the mean number of C2O42- coordinated in the complex anions. The molar ratio of R+ to Al(C2O4)sub(anti n)sup((2 anti n - 3)-) can also be assumed to be (2 anti n - 3):1 for the reaction of aluminum(III). The relation between the mean number of the ligand oxalate anion and the concentration of oxalate anion was obtained by the mole ratio method as well as the continuous variation method. The existence of the species such as UO2(C2O4)34- and UO2(C2O4)46- in (0.3 -- 5.0) x 10-3 M oxalate solutions (pH 6.5), and Al(C2O4)2- and Al(C2O4)33- in (0.15 -- 2.98) x 10-2 M oxalate solutions (pH 6.5) was ascertained. (auth.)