Rational Design of a 3D Crown-Based Material for the Selective Recovery of Silver Ions from Seawater and e-Waste

Silver recovery from sustainable sources such as seawater and e-waste is critical for the conservation of land-based resources and the reduction of the environmental impacts of e-waste disposal. However, the abundance of competing metal ions in seawater and in e-waste makes the recovery extremely challenging. Thus, to effectively capture silver ions under these conditions, the designing of materials with high selectivity, sufficient binding sites, and low affinity to competing metal ions is vital. Herein, we report the design and synthesis of a 3D-like Schiff-bridging crown-based material named AC5, for the selective recovery of Ag+ ions. Through this design, a significant enhancement in the silver ion recovery was achieved with an excellent removal efficiency of up to 99.9%, and a tremendous increase in selectivity of 400 000 - 900 000% when compared to the metal ions (Li+, Na+, K+, Mg2+, and Ca2+) found in seawater, and the heavy metal ions (Cu2+, Cd2+, Ni2+, and Pb2+) found in electronic wastes. Density functional theory and molceular dynamics simulations revealed that the structural geometry of AC5 favors high charge transfer, lowered global hardness, and enhanced ion-dipole attractions toward Ag+ ions, making the material an excellent candidate for the efficient recovery of silver from desalination brine and spent silver resources. In this study, a 3D-like Schiff-bridging crown ether (AC5) with carefully designed structural and charge transfer characteristics, lowered global hardness and enhanced dipole-dipole attractions is shown to demonstrate excellent potential for the recovery of Ag+ ions in both seawater and e-waste, achieving a remarkable recovery efficiency of 99.9%, and an enhanced selectivity up to 900 000%.image