A novel sponge-like composite biosorbent fabricated by sodium alginate and polyethyleneimine for uranium(VI) extraction from seawater.

Uranium extraction from seawater (UES) has important strategic significance for maintaining the sustainable development of nuclear energy. This article presents the preparation of a low-cost, efficient, and highly reusable biosorbent sodium alginate/polyethyleneimine (SA/PEI) through a simple one-step crosslinking process. The chemical crosslinking between PEI and SA provides biosorbent excellent mechanical strength and thermal stability. SA/PEI was characterized by using FTIR, XRD, TGA, EDS, XPS, SEM before and after adsorption of uranium. Thermodynamic research results show that the uranium adsorption of SA/PEI is a spontaneous, entropy increasing endothermic process. The adsorption fitted the pseudo-second-order kinetic model and Langmuir model with maximum adsorption capacity reach 353.09 mg g, illustrating that the adsorption mechanism is monolayer chemical adsorption. The interaction between SA/PEI and uranium is synergistic chelation by amino and carboxyl, which is consistent with the results calculated by DFT. After 14 days of adsorption in 100 L natural seawater, the adsorption capacity of SA/PEI was 3.58 mg g, with an average adsorption efficiency of 0.256 mg g day, which is faster than most reported alginate adsorbents. The cost of using SA/PEI to UES is $168 per kilogram of uranium. These results indicate that SA/PEI hydrogel has great potential in practical seawater application.