A DFT-designed neodymium ion-imprinted membrane with fouling resistance and high flux

Abstract

The rare earth metal neodymium (Nd) is widely used in advanced industries such as hybrid cars and aerospace. Therefore, recovering neodymium from wastewater presents valuable opportunities for secondary recycling. The recovery of Nd³⁺ from wastewater using ion imprinting technology (IIT) for efficient selective separation holds significant importance. In this study, hydrophilic Nd(III) ion-imprinted membranes, termed Nd(III)–P/P/TIIM, were synthesized using the IIT technique. Nd(III)–P/P/TIIM exhibited efficient and selective separation capabilities for Nd³⁺ with a remarkable retention rate of 95.68 % and a high water flux reaching up to 636.94 L·m⁻²·h⁻¹. Additionally, its relative selectivity coefficients for interfering ions ($K_{\text{La}}$, $K_{\text{Eu}}$, $K_{\text{Cu}}$) were 3.9, 29.5, and 37.9, respectively. Various analyses, including DFT calculations, HOMO and LUMO calculations, MEP images, and XPS spectroscopy, confirm that the mechanism of selective retention of Nd³⁺ by Nd(III)–P/P/TIIM in solution is due to Coulombic adsorption between the –COO⁻ anion and Nd³⁺ as well as an imprint memory effect. Even after undergoing three water-BSA cycles, the membrane maintained a water flux of 357.96 L·m⁻²·h⁻¹. The antifouling principle of Nd(III)–P/P/TIIM was investigated by XDLVO theory, attributed to the increase of electron donor tension (γ⁻) and Lewis acid-base interactions (${\Delta G}^{\text{AB}}$) at the membrane surface. This work provides an insightful guidance for engineering high-performance membranes and has the potential to provide an alternative method for recycling neodymium.