UO22+-imprinted thermoresponsive hydrogel for accumulation of uranium from seawater

A sodium alginate (ALG)-based UO22+-imprinted thermoresponsive hydrogel (SUIT) was prepared, with NIPAM as the starting monomer. On this basis, another hydrogel (SPUIT) was prepared with ɛ-polylysine (ɛ-PL) as a co-matrix to improve UO22+ adsorption capacity and stability of the hydrogel. The SUIT and SPUIT were characterized with FTIR, DSC, SEM, TGA, XPS, and Raman spectroscopy. The maximum adsorption capacity of SUIT and SPUIT to UO22+ was 137.43 mg/g and 205.99 mg/g, respectively. After simply washing the adsorbents with cold water, the desorption efficiency of SUIT and SPUIT reached 96.46% and 97.21%, respectively. The desorption efficiency of SUIT and SPUIT slightly decreased to 82.42% and 84.99% after 10 cycles of adsorption–desorption procedure. In the presence of other metal ions (Pb2+, Cu2+, Mg2+, Ca2+, UO22+, Cd2+, Na+, K+), the selectivity coefficients of SUIT and SPUIT for UO22+/Mn+ were in the range of 9.1–15.8 and 7.4–13.3. When tested with a 20 L real sea water, the adsorption capacity reached 58.24 µg/g for SUIT and 59.69 µg/g for SPUIT, demonstrating a high potential in accumulation of uranium. Moreover, the introduction of ɛ-PL enhanced the antibacterial activity and resistance to degradation of the hydrogel.