Efficient and selective capture of uranium by polyethyleneimine-modified chitosan composite microspheres from radioactive nuclear waste

Uranium extraction from radioactive nuclear waste is vital for sustainable energy supply and ecological security. Herein, a polyethyleneimine-chitosan composite microspheres n-PEI/ECH-CTS (n = 0.1, 0.2, 0.3, 0.4, 0.5) were synthetized for efficient and selective uranium adsorption. The prepared chitosan microspheres with uniform size, uniform dispersion and good mechanical strength combine cost-effectiveness and environmental benefits. The 0.4-PEI/ECH-CTS exhibits the highest adsorption capacity of 380.65 mg g-1 within only 4 h due to high nitrogen content of 6.57 mol kg-1. The DFT calculations confirms that the optimal coordination mode of UO22+ and 0.4-PEI/ECH-CTS is one UO22+ chelated with two -NH2 from two adsorption units, respectively. Adsorption efficiency of U(VI) from simulated nuclear wastewater achieves to 100%, and the Kd value is up to 1.1 x 104 mL g-1, which is 1.7 x 104-6.1 x 104 times that of coexisting ions. The CU(VI) reduces in simulated wastewater from 10.98 mg L-1 to 1 mu g L-1, which is well below the US Environmental Protection Agency uranium limits for drinking water (30 mu g L-1). Besides, 0.4-PEI/ECH-CTS still maintains above 95% adsorption efficiency after seven cycles. In short, the 0.4-PEI/ECH-CTS microspheres integrate high performance, practicality and costeffectiveness, which has great advantages in practical industrial applications.

Automated summary

Uranium extraction from radioactive nuclear waste is crucial for sustainable energy supply and ecological security. The synthesized 0.4-PEI/ECH-CTS composite microspheres show high uranium adsorption capacity of 380.65 mg g-1 within 4 hours due to their high nitrogen content. The microspheres exhibit excellent performance in removing U(VI) from simulated nuclear wastewater with 100% efficiency and reducing the concentration of CU(VI) to well below the limit set by the US Environmental Protection Agency for drinking water. The 0.4-PEI/ECH-CTS microspheres maintain above 95% adsorption efficiency after multiple cycles, making them highly suitable for practical industrial applications.