Enhancing uranium adsorption performance through the introduction of a electron conjugation system on amidoximated phenyl natural bamboo strips

Commencing with the goal of establishing a more stable coordination structure for uranium, our approach drew inspiration from the alternating single and double bonds found in benzene rings and amidoxime groups. A uranium adsorption material featuring a n-electron conjugated system is devised. This system is designed by grafting 2-cyanobenzaldehyde, 3-cyanobenzaldehyde, and 4-cyanobenzaldehyde onto bamboo strips (BS) via aldol condensation and hydrolysis reactions, resulting in the creation of 2-amidoxime phenyl BS (oBS-AO), 3amidoxime phenyl BS (mBS-AO), and 4-amidoxime phenyl BS (pBS-AO). Among these, oBS-AO exhibits not only the highest uranium adsorption performance (224.6 mg g-1 at pH = 6 and 1.3 mg g-1 in artificial simulated seawater) but also features the most robust n-electron conjugated system, as confirmed by computational and simulation data. Notably, the uranium adsorption capacity of mBS-AO is approximately 46.7 times that of vanadium in ion competition experiments simulating seawater conditions. To delve further into the adsorption mechanism, the role of electrostatic interactions and optimized simulated coordination structures is explored. It becomes evident that the primary adsorption mechanism relies on the formation of a pentacoordination structure, and the stability of this coordination structure iss directly influenced by the strength of the n-electron conjugated system. Furthermore, the double bridging effect of hydrogen bonds serves to further stabilize the coordination structure, facilitating the specific and selective adsorption of uranium.