Polymeric nano-films with spatially arranged compartments for uranium recovery from seawater

Abstract

Polymeric thin film composite (TFC) membranes are well-known for their application in aqueous separation processes, these TFC membranes have the proven advantage of such demanding stability, tunable porosity and possibility of incorporating the selective binding sites for one of the challenging chemical separation of Uranium (U) from seawater. Here, in this work we report the preparation of polycondensation polymer (PAR) of a pre-synthesized schiff base having the binding pocket for U, via industrially relevant interfacial polymerization. The large area polymeric nano-films (pTF) of conjugated schiff-base have been prepared at the solvent-non-solvent interface yield the nano-film of tunable thickness ≥ 22 nm. The conjugated monomer develops the electrical double layer with Debye length (λD) < 1 nm thickness, helps in localizing the negative charge on the surface, which polarizes the ions largely present in seawater. The pTF and PAR are characterized for its composition, surface charge, hydrophilicity and microscopic properties. The pTF of ∼22 nm thickness delivered high efficiency of U extraction from natural seawater (UES) ∼16.5 ± 0.7 mg/g in 30 days. It showed >2 times high U to V (Vanadium) selectivity ratio, fast UES kinetics of 0.6 mg/g/d, and reasonable service life of 5 adsorption–desorption cycles. The binding analysis suggests that network of polymeric chains containing conjugated schiff base in pTF provided the micro-pores, decorated with the spatially arranged binding pockets to adsorb U possibly in its octahedral geometry.