Synthesis of hollow organosiliceous spheres for volatile organic compound removal

Abstract

Hollow organosiliceous sphere (HOS) materials have been successfully synthesized by a co-condensation method with tetraethylorthosilicate (TEOS) and organosilane (1,2-bis(triethoxysilyl)ethane, BTSE) as mixed silica sources under acidic conditions. The application of HOSs as adsorbents for the volatile organic compound (VOC) abatement was demonstrated. The HOSs were characterized by transmission electron microscopy (TEM), N₂ sorption isotherms, FT-IR spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results indicated that all samples showed a uniform hollow mesostructure and the organic groups were chemically incorporated into the walls of HOSs. The static adsorption and stability behaviors of water vapor, n-hexane and 93# gasoline on HOSs were investigated, with commercial silica gel (SG) and activated carbon (AC) as references. It was found that the sample with an initial molar ratio BTSE/(BTSE + TEOS) of 25% (HOS-25%) had the largest VOC adsorption capacity (1.36 g g⁻¹n-hexane and 1.35 g g⁻¹ 93# gasoline) and the smallest water vapor adsorption capacity (0.0120 g g⁻¹) under static adsorption conditions. The dynamic adsorption behaviors of n-hexane on HOS-25% were evaluated via breakthrough curves. The dynamic adsorption capacities of n-hexane are in the following order: SG < AC < HOS-25% and the stability is in the order of AC < SG < HOS-25%. The larger dynamic VOC capacity of the HOSs may be attributed to the synergetic effect between the unique morphology and hybrid walls. The static and dynamic n-hexane and water vapor competitive adsorption results suggested that HOS-25% had a much higher adsorption tendency for VOCs over water vapor. The HOSs with high hydrophobicity, large VOC removal capacity and excellent recyclability show great potential for VOC controlling.