Use of apatite and bone char for the removal of soluble radionuclides in authentic and simulated doe groundwater (Reprinted from Advances in Environmental Research, vol 3, pg 488-498, 2000)

The phosphate-based mineral phases Apatite II and bone char are shown to be effective for the removal of select heavy metal impurities in groundwater. The performance of select apatite-based products is compared with that of other candidate sorption media (including granular activated carbon and ani on exchange resin) for the removal of soluble uranium ion in synthetic Depa rtment of Energy (DOE) Site groundwater supplemented with varying levels of interfering nitrate ion. Apatite has a greater affinity for U(VI), especia lly in the presence of nitrate ion, as evidenced by a larger value for the conditional distribution coefficient (Kd) in batch test experiments. Contac t of uranyl nitrate solution with apatite is shown to produce highly insolu ble mineral phases of the autunite group (calcium uranyl phosphate hydrates ). The activity of soluble uranium in contact with excess Apatite II reagen t is equivalent to similar to 2-3 mu g/L (i.e., 2-3 parts per billion) uran ium. We also show that Apatite II is effective for the removal of soluble c erium ion, a nonradiological surrogate used to mimic the behavior of pluton ium and other actinides or transuranic elements.