Tunable adsorption behavior of silica materials in the removal of dense non-aqueous phase liquids

Mesoporous silica material has dual characteristics including adsorption of organic contaminants and transport through the sediments, making it an ideal material as a platform for zerovalent iron particles in the in situ remediation of dense non-aqueous phase liquids such as trichloroethylene. In this paper, tunable adsorption behavior of silica materials was quantitatively investigated by batches of equilibrium experiments. Significant enhancement in adsorption capacity was observed on mesoporous organo-silica particles as a consequence of the functionalization of particle surface from hydrophilicity to hydrophobicity. The fact that there is a wide difference in adsorption capacities between the non-functionalized mesoporous silica (MCM-41) and the alkyl-functionalized mesoporous silica prompted a study to control adsorption levels by simply adjusting the amount of methyl triethoxysilane (MTES) precursor in a mixture of MTES and tetramethoxysilane. In comparison with the most commonly used adsorbent activated carbon, the higher yield of adsorbent of 83 ± 2.6% was observed for mesoporous methyl silica particles. Particle characterizations were performed by means of X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, Brunauer–Emmett–Teller, thermogravimetric analysis and Fourier transform infrared measurements.