Anti-fouling and thermosensitive ion-imprinted nanocomposite membranes based on grapheme oxide and silicon dioxide for selectively separating europium ions.

The increasing amount of europium in aqueous environment from rare earth industry has become a serious environmental challenge. Significant efforts have been focused on ion-imprinting membranes (IIMs) for selective separation of ions from analogues. Based on ion-imprinting technique, we have developed Eu-imprinted nanocomposite membranes (Eu-IIMs) for selectively separating Eu from La, Gd and Sm. Polydopamine (pDA) was previously synthesized on basal membranes to augment the interfacial adhesion. Grapheme oxide (GO) and modified silicon dioxide (kSiO) were synergistically stacked on pDA-modified substrates to form hydrophilic nanocomposite membranes. Ag nanoparticles were modified on the surface to enhance anti-fouling performance. The temperature-controlled selective recognition sites were formed using N-isopropylacrylamide (NIPAm) and acrylamide (Am) as functional monomers as well as europium ions as templates by RAFT (reversible addition-fragmentation chain transfer) method. Large enhanced Eu-rebinding capacity (101.14 mg g), adsorptive selectivity (1.82, 1.57, 1.45 for Eu/La, Eu/Gd, Eu/Sm) and permselectivity (3.82, 3.47, 3.34 for La/Eu, Gd/Eu, Sm/Eu) were achieved on Eu-IIMs with superior regeneration performance. Additionally, the negligible damage of the membranes after buried for 20 d indicated the superior anti-fouling property of the Eu-IIMs. The ion-imprinted nanocomposite membranes synthesized in this work have shown great potentials for selective separation of rare earth ions.