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 within only 4 h due to high nitrogen content of 6.57 mol kg. The DFT calculations confirms that the optimal coordination mode of UO and 0.4-PEI/ECH-CTS is one UO chelated with two -NH from two adsorption units, respectively. Adsorption efficiency of U(VI) from simulated nuclear wastewater achieves to 100%, and the K value is up to 1.1 × 10 mL g, which is 1.7 × 10-6.1 × 10 times that of coexisting ions. The C reduces in simulated wastewater from 10.98 mg L to 1 μg L, which is well below the US Environmental Protection Agency uranium limits for drinking water (30 μg L). 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 cost-effectiveness, which has great advantages in practical industrial applications.