Complex formation of Uranium(IV) with Phosphate studied by laser-induced photoacoustic spetrosopy


Complex formation of Uranium(IV) with Phosphate studied by laser-induced photoacoustic spetrosopy

Geipel, G.; Bernhard, G.; Brendler, V.; Rutsch, M.; Nitsche, H.

Uranium can occur in reducing phosphate-containing environments as uranium(IV)-hadrogenphosphate, U(HPO4)2.4H2O. No thermodynamic complex formation constants are available for the uranium(IV)-phosphate complexes because of their low water solubility. For example, the solubility product /1/ of U(HPO4)2.4H2O limits the uranium(IV) concentration in 1 M perchloric acid to less than 1.2 x 10-4 M. We studied the formation of this complex at uranium concentrations between 2x10-6 M and 1x10-4M by Laser-Induced Photoacoustic Spectroscopy in acid media. To determine the complex formation constant we measured and analyzed the spectra from 610 nm to 690 nm. The spectra were corrected for the absorption of the solvent water. The solvated uranium(IV) shows a very intensive absorption band with a maximum at 649.8 nm and a smaller maximum at 671.9 nm. We found a shoulder at 630.0 nm by deconvoluting the absorption spectrum. The spectrum changes with increasing phosphate concentration. At a total phosphate concentration of 1.5x10-3M, we found maxima at 656.6 nm and 667.0 nm. Additionally a shoulder at 645.0 nm is found. Two isosbestic points were determined at 661.4 nm and 669.4 nm. Results will be presented for the determination of the formation equilibrium and the complex formation constant(s).

  • Lecture (Conference)
    Migration´99, Village

Permalink: https://www.hzdr.de/publications/Publ-1499
Publ.-Id: 1499