Phenyl-bridged silica aerogels with enhanced textural and mechanical properties for heavy metal removal

Abstract

The refluxing method was used to prepare a bridged silicon precursor, in which different numbers of benzene rings (hydroquinone and 4,4′-dihydroxybiphenyl as the organic components) were added as bridges between silica clusters. Using this precursor, phenyl-bridged silica aerogels were synthesized via the sol-gel method, followed by supercritical drying. The phenyl-bridged silica aerogels possessed a homogeneous cage-like network with a high specific surface area (1510 m²/g), low bulk density, and high strength (1.79 MPa). Further, the phenyl-bridged silica aerogels were amino functionalized to remove heavy metal ions. The removal efficiencies of these amino-modified aerogels for Pb²⁺ via adsorption were found to be high (99.95 %) owing to the high-surface-area nanostructured silica network. The maximum adsorption capacity fitted by the Langmuir adsorption model was 704.225 mg g⁻¹ and the outstanding selectivity for Pb²⁺. Hence, phenyl-bridged amino-modified silica aerogels have high potential for use in applications such as removing heavy metal ions.