Article

Decontamination of Uranium-Contaminated Steel Surfaces by Hydroxycarboxylic Acid with Uranium Recovery

Environmental Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, and Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York 11794
Environ. Sci. Technol., 2005, 39 (13), pp 5015–5021
DOI: 10.1021/es048887c
Publication Date (Web): May 19, 2005
Copyright © 2005 American Chemical Society

Abstract

We 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.

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Article Views: 460 Times
Received 17 July 2004
Date accepted 1 April 2005
Published online 19 May 2005
Published in print 1 July 2005
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