Novel thermo-sensitive core–shell surface ion-imprinted polymers based on SiO2 for the selective adsorption of Nd(iii)

Abstract

Thermo-sensitive materials are attracting increasing interest and have wide application prospects, with N-isopropylacrylamide (NIPAM) being a typical example. In this study, NIPAM was utilized as an ionic cross-linker, while 2-acetamidoacrylic acid (AAA), known for its high coordination capacity with Nd³⁺ ions, was selected as the functional monomer. An ionic imprinted polymer (Nd(III)-IIP) with Nd³⁺ vacancies was synthesized through surface imprinting on N-propylmaleamic acid-functionalized silica gel (SG-PMA). The comprehensive performance of Nd(III)-IIP was evaluated, revealing that it adsorbs Nd³⁺ from aqueous solutions with both high efficiency and selectivity. Additionally, Nd(III)-IIP contains thermal recognition sites, and the structure of the imprinting cavity can be adjusted by varying the temperature. At 30 °C, the adsorption capacity of Nd(III)-IIP for Nd³⁺ was 37.94 mg g⁻¹, which was significantly higher than that at other temperatures. In the presence of interfering ions such as Cu(II), La(III), and Eu(III), the separation coefficient (D) of Nd(III)-IIP was 774.96 mL g⁻¹. After 10 cycles of water adsorption/desorption at 0 °C, Nd(III)-IIP retained 70% of its original adsorption capacity. Additionally, elution analysis using energy dispersive spectroscopy (EDS) spectra confirmed that no residual Nd³⁺ remained in the material. This indicates that the adsorption performance of Nd(III)-IIP achieves “temperature-locked” control, and regeneration and recycling can be achieved by temperature adjustment without the need for additional chemical reagents.