es048887c_si_001.pdf (25.7 kB)
Decontamination of Uranium-Contaminated Steel Surfaces by Hydroxycarboxylic Acid with Uranium Recovery
journal contribution
posted on 2005-07-01, 00:00 authored by J. Francis, C. J. Dodge, J. A. McDonald, G. P. HaladaWe developed a simple, safe method to remove uranium
from contaminated metallic surfaces so that the materials
can be recycled or disposed of as low-level radioactive
or nonradioactive waste. Surface analysis of rusted uranium-contaminated plain carbon-steel coupons by X-ray
photoelectron spectroscopy and Rutherford backscattering
spectroscopy showed that uranium was predominantly
associated with ferrihydrite, lepidocrocite, and magnetite,
or occluded in the matrix of the corrosion product as
uranyl hydroxide and schoepite (UO3·2H2O). Citric acid
formulations, consisting of oxalic acid−hydrogen peroxide−citric acid (OPC) or citric acid−hydrogen peroxide−citric acid (CPC), were used to remove uranium from the
coupons. The efficiency of uranium removal varied from 68%
to 94% depending on the extent of corrosion, the
association of uranium with the iron oxide matrix, and the
accessibility of the occluded contaminant. Decontaminated
coupons clearly showed evidence of the extensive removal
of rust and uranium. The waste solutions containing
uranium and iron from decontamination by OPC and CPC
were treated first by subjecting them to biodegradation
followed by photodegradation. Biodegradation of a CPC
solution by Pseudomonas fluorescens resulted in the
degradation of the citric acid with concomitant precipitation
of Fe (>96%), whereas U that remained in solution was
recovered (>99%) by photodegradation as schoepite. In
contrast, in an OPC solution citric acid was biodegraded but
not oxalic acid, and both Fe and U remained in solution.
Photodegradation of this OPC solution resulted in the
precipitation of iron as ferrihydrite and uranium as uranyl
hydroxide.