Dual-template ion-imprinted mesoporous membranes for selective adsorption of Nd(III)

As contemporary high-tech advancements progress, the strategic significance of rare earth elements is increasingly highlighted. Beyond mitigating supply risks, their recovery from wastewater offers direct benefits for environmental protection and human health, making it an indispensable practice. In this work, dual-template ion-imprinted mesoporous membranes (IMMs) were prepared by direct copolymerization and evaporation-induced self-assembly with chitin nanocrystals as the structural template, Nd³⁺ as the ion-imprinting template, and iminodiacetic acid-modified silane coupling agent as the functional monomer for the selective adsorption of Nd³⁺. The influence of structural porosity, pH, initial ion concentration, adsorption time, and temperature on the adsorption performance was systematically characterized. It was found that IMMs had an average pore size and a specific surface area of 11.20 nm and 221.30 m² g^-1, respectively. At pH = 5 and 25 °C, IMMs had the maximum adsorption capacity for Nd³⁺ at 117 mg g^-1 at a solid-to-liquid ratio (mg:mL) of 1:1, and the selective factors (SF) for Nd³⁺ in the presence of Al³⁺, Fe³⁺, and La³⁺ were 74.14, 23.86, and 15.93, respectively, which is advantageous compared to the other reported ion-imprinted adsorbents. The selective adsorption of Nd³⁺ was also confirmed with the industrial ore leaching wastewater. The adsorption isotherm followed the Langmuir model with pseudo-second-order kinetics, and the adsorption process was exothermic. The proposed IMMs are easy to prepare and collect, which is of practical importance for large-scale applications.