Uranium adsorption by biosourced hydroxyapatite with a large specific surface area

Uranium (U), primarily known for its radioactivity in nuclear applications, is more chemically toxic than radioactive owing to its extremely long half-life of ∼4.5 billion years. The most common route of exposure to living beings is through the consumption of contaminated water. Hence, the development of treatment techniques to extract dissolved U from aqueous systems is of great interest. Hydroxyapatite (HA), a strong uranium adsorbent, functions based on three different mechanisms depending on the pH conditions: dissolution/precipitation, surface complexation, and ion substitution. HA with a large specific surface area recovered via the oxidative hydrothermal treatment (OHT) of bovine bones was compared with a commercial HA and HA obtained via bovine bone calcination. The large specific surface area of the OHT-derived HA exhibits >85% U removal efficiency across the entire studied pH range of 4-8. HA also exhibits the highest maximum extraction capacity at pH 4 (1148 ± 17 mg g^-1), outperforming most earlier reported adsorbents.