Enhancement of adsorptive activity for removing heavy metal ions via amidoxime functionalized silica-based aerogels: performance, mechanism and LCA evaluation

In this study, a novel amidoxime-functionalized silica-based aerogel (ASA-X) with multi-site adsorption capabilities was successfully synthesized. The integration of amidoxime groups into the silica aerogel framework facilitated the decontamination of Pb (II) and Cu (II) solutions. Morphological and structural characterizations revealed a nanoparticle-assembled 3D framework structure, featuring mesoporous and macroporous architectures. Batch adsorption experiments demonstrated exceptional adsorption performance of 252.55 mg/g and 247.81 mg/g for Pb (II) and Cu (II). Four adsorption isotherm and kinetic models confirmed chemisorption as the dominant mechanism, and thermodynamic analysis indicated a spontaneous and exothermic process. Synergistic XPS/DFT investigations elucidated that metal ion adsorption primarily stemmed from coordination effects between amidoxime groups and metal ions. Notably, ASA-3 exhibited pronounced selectivity toward Pb (II) and Cu (II) in aqueous solutions containing competitive impurity ions, indicating effective chelation via its amidoxime ligands. The adsorbent maintains high removal efficiency for both metal ions even after 12 consecutive adsorption–desorption cycles, demonstrating excellent reusability. A life cycle assessment (LCA) proposed a more environmentally friendly preparation strategy. This study proposes an innovative strategy to optimize adsorbent efficacy and advance sustainable remediation of heavy metal-contaminated industrial wastewater.