Salt-shrinkage resistant poly(amidoxime) adsorbent for improved extraction of uranium from seawater

Utilization of the seawater uranium (U) resource is a prospective strategy to satisfy the requirements of nuclear energy industry. Poly(amidoxime) (PAO)-based adsorbents are the most prospective candidates for extracting seawater U resource. However, owing to its innate shortcoming of salt shrinkage in seawater, the channels between the polymer chains in PAO-based adsorbents are shrinkage, hindering the entry of uranyl ions into the adsorbent. Therefore, amidoxime groups in PAO-based adsorbents are not utilized efficiently. Herein, a universally applicable pre-hydrolysis strategy is designed to boost the U extraction performance of PAO-based adsorbents. Pre-hydrolyzed polyacrylonitrile is used to fabricate PAO with higher hydrophilicity, namely h-PAO. Due to the existence of more hydrophilic groups generated by the pre-hydrolysis process, h-PAO hydrogel exhibits enhanced interaction with water and reduced salt-shrinkage behavior compared with that of PAO hydrogel. As a result, h-PAO hydrogel exhibits increased (6.5-fold) seawater migration ability to facilitate the transport of uranyl ions to the functional groups inside the adsorbent. In filtered real seawater, h-PAO hydrogel shows 60.3% enhanced U extraction capacity, which is 9.86 mg g−1, and more than 1-fold accelerated U extraction rate. Collectively, our results indicate that the pre-hydrolysis strategy is a promising approach to boost the U extraction performance of PAO-based adsorbents in real seawater.