From dental waste to uranium adsorbent: A sustainable strategy for hydroxyapatite recovery and radioactive water decontamination

As pathological medical waste, extracted human teeth are typically disposed of by high-temperature incineration. This method is not only costly, but also results in the unnecessary loss of valuable hydroxyapatite (HA) resources. Meanwhile, the contamination of water by radioactive U(VI) remains a major environmental challenge for the nuclear industry. In this study, a sustainable strategy was proposed, in which discarded extracted teeth were converted via a mild pretreatment process into a high-performance hydroxyapatite adsorbent (denoted as d-HA) that retained the natural hierarchical pore structure and exhibited excellent adsorption performance for the efficient removal of U(VI) from water. The results showed that d-HA achieved a U(VI) removal efficiency of up to 98.09% at pH = 3. Its adsorption behavior followed the pseudo-second-order kinetic model and Langmuir isotherm model, with a maximum adsorption capacity of 808.99 mg/g, which was superior to that of most similar adsorbents reported in the literature. Characterization by SEM, XPS, FTIR, and DFT showed that the adsorption mechanism was mainly governed by chemical complexation between UO 2 2+ and surface PO 4 3− groups, accompanied by partial ion exchange. D-HA still maintained a selective adsorption capacity of 98.97% for U(VI) in simulated wastewater containing various competing ions. Elution with 0.5 M HNO 3 allowed the adsorption capacity to remain at 61.90% of its initial value after 8 cycles, indicating good reusability and potential for practical applications. This study demonstrates a green and low-cost approach for converting medical waste into a high-performance uranium adsorbent, offering a sustainable solution for the treatment of radioactive wastewater.