Voltammetric study of uranyl-selenium interactions

Uranyl-selenium interactions were studied at two different ionic strengths (I = 0.1 and 3.0 mol/l) using square wave voltammetry. The uranyl(+6) reduc tion signal is only slightly affected by selenium(+4) reduction to HgSe, wh ich appears in virtually the same potential range. On the other hand, the h eight and shape of the selenium stripping peak (which corresponds to dissol ution of accumulated HgSe) can be significantly changed by the uranyl(+6) c oncentration in the solution. The type and magnitude of such effects are hi ghly dependent on the ionic strength. Asa result of uranyl(+6) interaction with selenium(+6), a coordination species UO2SeO4 is formed, whose stabilit y constant at I = 3 mol/l (log beta(1) = 1.57 +/- 0.01) is in very good agr eement with the literature value based on spectrophotometric data. The pres ence of higher complexes could not be confirmed unambiguously. (C)2000 Else vier Science B.V. All rights reserved.