Uranium Dissolution by Biosiderophore Desferrioxamine.

Biosiderophore Desferrioxamine B (DFB) is a trihydroxamate ligand that chelates with metals through hydroxamate coordination. Complexation of DFB with U can be utilized in decontamination of passivity layers in metal wastes. We reacted U(VI) with Fe(0) at variable conditions and followed with dissolution by DFB as a function of pH, molality and temperature. The objectives were to determine the structure and speciation of solution and solid phases of U and to assess the effectiveness of DFB in U dissolution. The solids were characterized using X-ray Microscopy. Typically, pH 5 favored >90% of solid phase formation. The solution U disappearance kinetics followed a first order reaction and the solid phase formation appeared to be a combination of partial reduction, adsorption and precipitation processes, depending on the pH and molal conditions. Saturation index computation suggested plausible formation of Schoepite and some U oxides. Spatial elemental mapping revealed that relative distributions of U and Fe varied with solid formation conditions. The Fe edges showed patterns for both 0 and III valence states. The U edge was observed mostly at VI valence state albeit with the presence of some IV state typically at lower molality and pH conditions of the formation media. Schoepite was detected in post-DFB-dissolution residues, which originated from both U(IV) and U(VI) type parent solids. DFB dissolved up to 40 times more U than water. Structural mapping and identification of solid phase species of uranium associated with iron are critical in understanding the remediation chemistry of the passivity layers. The data indicated that DFB effectively dissolved U formed under diverse chemical conditions.