Fabrication of ion imprinted chitosan-polyethylene glycol-polyvinyl alcohol hybrid membrane for selective recovery of Nd(III).

Reclamation of rare earths from secondary sources is in line with both environmental remediation and sustainable utilization of rare earth resources. Herein, neodymium Nd(III) imprinted polyethylene glycol-polyvinyl alcohol hybrid membrane (IIP-CS-PEG-PVA) with high selectivity, increased specific surface area, acid stability and easy recyclability was constructed using chitosan (CS) as functional monomer, polyethylene glycol (PEG) as porogenic agent, polyvinyl alcohol (PVA) as filmogen, and Nd(III) as template ion. Batch adsorption indicates, adsorption of IIP-CS-PEG-PVA for Nd(III) is induced by electrostatic interaction, reaching rapid equilibration in 35 min at pH = 5. The maximum adsorption capacity determined by Langmuir fitting is 221.73 mg·g-1. Owing to its ion imprinting sites, IIP-CS-PEG-PVA exhibits selectivity coefficient 3.47, 3.72, 9.71, 8.33 towards Nd(III) for binary solution Nd/Eu, Nd/Dy, Nd/Cu, Nd/Cr, respectively. Being as a membrane, IIP-CS-PEG-PVA can be easily recovered for cyclic adsorption, whereby retaining adsorption quantity 73.95 mg·g-1 on Nd(III) in five consecutive cycles. Compared with other adsorbents, IIP-CS-PEG-PVA exhibits fast equilibrium, high adsorption capacity and selectivity towards Nd(III). For adsorption mechanism, versatile functional groups -OH, -NH2, -C(=O)NH-, C-O-C in IIP-CS-PEG-PVA provides heterogeneous affinity for Nd(III), giving rise to chemical adsorption. This work provides a novel strategy for fabricating bio adsorbent towards selective recovery of Nd(III).