Macroporous hydrogel membrane by cooperative reaming for highly efficient uranium extraction from seawater

As nuclear power plant fuel, nearly 4.5 billion tons of uranium is reserved in the ocean with a low concentration of 3.3 ppb. Uranium capture from natural seawater relies heavily on the development of highly efficient uranium adsorbent. By combination of the water-soluble pore-forming agent (sodium bicarbonate, NaHCO3) and alkali treatment technology, a novel macroporous polyamidoxime (MP-PAO) hydrogel membrane is prepared for highly efficient uranium sorption. The macropores with a size of about 40 µm in diameter contribute to the exposure of previously hidden coordination bond sites and fast diffusion of uranyl ion. As a result, the MP-PAO membrane adsorbent delivers superior uranium sorption capacity of 5.80 mg-U/g-Ads, almost 1.76 times that of the pristine polyamidoxime (PAO) membrane adsorbent. Strikingly, the adsorption equilibrium of uranium on the MP-PAO membrane can be reached within 24 days. The adsorption rate of MP-PAO membrane is 14.29% faster than that of the reference PAO membrane. In addition, the MP-PAO membrane also shows a good reusability and long service life. The strategy applied in this work is widely suitable for the preparation of macroporous adsorbents. MP-PAO membrane holds tremendous potential for uranium capture from natural seawater.