Synthesis of Ag nanoparticles encapsulated in hollow silica spheres for efficient and selective removal of low-concentrated sulfur compounds

Abstract

Silver nanoparticles (AgNPs) encapsulated in porous materials such as mesoporous silica and zeolite exhibit high adsorption toward sulfur compounds owing to their defined porous structure. In this study, we report the synthesis of AgNPs encapsulated in hollow silica spheres, which act as efficient adsorbents for the removal of low-concentrated sulfur compounds. Hollow silica spheres bearing propyl amine groups inside a silica shell (NH₂–HSS) were fabricated utilizing an oil-in-water (O/W) microemulsion as a template and a subsequent solvent extraction process. AgNPs were selectively deposited inside the NH₂–HSS with the assistance of microwave irradiation. The AgNPs encapsulated within NH₂–HSS (Ag@HSS) exhibit adsorption toward several sulfur compounds such as H₂S and tert-butylmercaptan (TBM) with low-concentration (45 ppm) at ambient conditions, while prohibiting the adsorption of protein molecules that potentially deactivate AgNPs as inhibitors due to the protective effect of the silica shell. Ag@HSS displayed promising reusability; it retained its initial adsorption performance even after successive high temperature regeneration cycles, suggesting that this material is a promising adsorbent for the efficient and selective removal of volatile sulfur compounds.