Facile and scalable synthesis of bio-based adsorbents from tannin for economical uranium extraction from seawater

Extracting uranium from seawater through adsorption is an effective approach to ensure the sustainable development of nuclear energy. However, the currently developed adsorbents suffer from high cost or low adsorption efficiency. Herein, a low-cost and easily prepared bio-based adsorbent (TBAs) was synthesized from tannin via the phenol-aldehyde condensation. The preparation cost of TBAs was only $1.67 kg −1 , which was close to those of traditional low-cost adsorbents (e.g. activated carbons and zeolites). Moreover, TBAs had abundant active phenolic hydroxyl groups, which contributed to the high affinity toward uranyl ions. As a result, TBAs exhibited a high uptake of 897 mg g −1 in uranium spiked solution and good selectivity against common competing metal ions. Additionally, TBAs also displayed good reusability with an 8 % reduction in uranium adsorption capacity after twenty adsorption-desorption cycles. For practical uranium extraction from natural seawater, TBAs could be loaded on melamine foam to obtain macroscopic adsorbent (MF@TBAs). An extraction capacity of 4.2 mg g −1 from natural seawater within 16 days could be achieved, which surpassed most of reported bio-adsorbents. Significantly, the total economic cost of uranium extraction by MF@TBAs was $43.7–62.6 per kg of uranium, lower than that of currently available uranium adsorbents. All the above results indicate that TBAs have great potential in the field of economical uranium extraction from seawater.