Super-fast and highly efficient extraction of uranium from water by a surface-acidified hydroxyapatite

The elimination of U(VI) from acidic nuclear wastewater is important for solving the problems in environmental and energy fields. However, the adsorbents used for U(VI) extraction/removal usually undergo the issues of high cost, low efficiency, and long adsorption time. In this work, surface-acidified hydroxyapatite (SAHAP) powders were obtained by soaking chicken leg bone in acetic acid combined with hydrothermal treatment, which shows super fast removal/extraction capacity of U(VI) from the solution. The surface of the SAHAP is highly acidified by large quantities of hydrogen phosphate radicals. The characterization and mechanistic investigations indicate that the U(VI) substitute with Ca²⁺/H⁺ via an ion-exchange related monolayer chemisorption process. At room temperature, over 99 % of U(VI) could be sequestrated by SAHAP within 20 s at pH 4.0, and the extraction amount could reach 1270 mg/g. Moreover, the SAHAP shows great application potential in the removal/extraction of U(VI) from seawater, and 25 mM CO₃^2- ions could only reduce the adsorption ability by 4.18 % at pH 4.0. This study provides a new approach to fabricating adsorbents for highly effective, selective and low-cost extraction of U(VI) from wastewater.