Uranium-238 (238U), a long-lived radiometal, is widespread in the environment as a result of both naturally occurring processes and anthropogenic processes. Naturally occurring processes include the formation and sorption of U in sediments and rocks such as the Mancos Shale, as well as oxidative dissolution, where naturally occurring nitrates modify the solubility of uranium and therefore increase its concentration in drinking water. On the other side of the spectrum are the anthropogenic contaminations of U, which result in the liberation of quadrillions of becquerel and tons of nuclear materials into the environment. This is of interest because the intake, whether through ingestion or inhalation, of large amounts of U is a major threat to humans, and its toxicity is considered as mainly chemical rather than radiological. Therefore, a way to remove uranium that has either been ingested by humans, is present in uranium contaminated water, or found in the air, is sorely needed. In this study, the uranium uptake in hydroxyapatite (HAP) a compound found in human bone and teeth, was observed, since the first barrier for U uptake as a result of U transport through contaminated water is the teeth. Uranium is transported in groundwater primarily as dissolved uranyl (UO22+), which can find itself in drinkable water supplies. High levels of uranium sorption with synthetic HAP were previously reported. In this present work, the influence of pH, kinetics, U concentration and metal competition on the uptake of U in HAP present in bone and teeth was investigated. Our results show that the influence of pH (pH of human saliva, 6.7-7.4) on the uptake of uranyl is negligible. Furthermore, it was discovered that the kinetics of uranyl uptake are extremely fast; by one second of exposure, 92% of uranium was uptaken by HAP. Finally, high sorption of uranium by HAP was observed, which was consistent with previously reported data. Another series of in vitro tests were performed with real teeth as targets. It was found that with a 10 ppm U in PBS solution adjusted to physiological pH, 10% of the uranyl was uptaken by the tooth. Furthermore, among several tested wash solutions, it was found that a common commercially available carbonate solution was able to remove all uptaken uranyl from the target teeth. The ultimate goal with this information is to develop a solution, safe for human intake, which will completely remove uranium from teeth and other target tissues and organs.

Toward a novel treatment for the removal of deposited uranium in case of human contamination

2019 Spring National Meeting

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