X-ray photoelectron spectroscopy investigation of the interaction of U(VI)and Fe(III) with natural humic acid in aqueous solutions

Complexes of U(VI) and Fe(III) with natural humic acid (NHA) were studied b y X-ray photoelectron spectroscopy (XPS). It follows from the analysis of t he uranium and iron concentrations at the surface and in the bulk of the hu mates that the reaction in solution is heterogeneous. The NHA reacts as a p article. In solutions containing either U(VI) or Fe(III), NHA reacts simila r with Fe(III) and U(VI). However, in a mixed solution of Fe(III) and U(VI) , NHA reacts predominantly with iron. In comparison to Fe(III) complexes, t he complexes with U(VI) are formed mostly in the inner of the NHA particle. Therefore, the concentration ratio U/Fe as measured by XPS increases by po wdering of the particles. Salts of Fe(III) can be used to inhibit the urani um migration in form of its soluble humates.