Interaction of aluminium(III) with uranyl ions in the course of joint hydrolysis

Interaction of U(VI) with Al(III) in solutions at pH greater than or equal to 2 and in precipitates obtained at pH greater than or equal to 5 was stud ied using spectrophotometry, luminescence, and IR spectroscopy. It was show n that in the range of pH 3-4, hydrolyzed forms of uranyl and of aluminium come into interaction. The mixed hydroxoaqua complexes (H2O)(3)UO2(mu -OH)( 2)Al(H2O)(4)(3+),(H2O)(3)UO2(mu -OH)(2)Al(OH)(H2O)(3)(2+), or (H2O)(4)UO2OA l(OH)(H2O)(4)(2+) are likely to form in the solution. With an increase in p H, mixed polymers of a large size (oligomers) can form which further take p art in the precipitate formation. The reaction between U(VI) and AI(III) in precipitates is confirmed by the data of IR spectroscopy and by the change s in the physico-chemical properties of these precipitates as compared with the properties of a mechanical mixture of separately precipitated uranium and aluminium. The important role of the oligomeric mixed forms in the form ation of precipitate remains at pH levels varying from 5 to 14.