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Government researchers have found a simple, safe way of removing radioactive uranium from contaminated surfaces, soil and incinerator ash by using citric acid.

“Until now, decontamination of radionuclides from buildings and other surfaces left contaminated by radiological incidents has been a major environmental challenge,” said A.J. Francis, a scientist with the Brookhaven National Laboratory.

Francis and fellow scientists Cleveland Dodge and Gary Halada developed an environmentally friendly green-chemistry process that uses all naturally occurring materials, namely citric acid, common soil bacteria and sunlight.

Currently, removing uranium from contaminated metal surfaces requires sand blasting, chemical extraction and electro-chemical dissolution — methods that generate secondary waste streams, compounding the problem.

“In the event of a radiological incident, such as a dirty bomb, this new technology can be used to clean up contaminated materials,” Francis said. The comprehensive process also can treat the secondary waste generated by the current treatment process, resulting in waste minimization.

Using a synchrotron light source (a source of intense x-rays, ultraviolet, and infrared light), the scientists systematically examined the contaminated materials at the molecular level, investigating the association of uranium before and after treatment with the citric acid formulations.

The efficiency of uranium removal ranged from 68% to 94%, depending on the age and extent of corrosion, according to Francis.

Wastewater produced by the process is then subjected to biodegradation, followed by photodegradation, all of which minimizes production of secondary waste and allows the uranium to be recovered. The patented process also can be used to remove toxic metals and radionuclides from contaminated soil, waste and incinerator ash.