The fate and transport of the SiO2 nanoparticles in a granular activated carbon bed and their impact on the removal of VOCs.

Adsorption isotherm, adsorption kinetics and column breakthrough experiments evaluating trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) were conducted in the presence and absence of silica nanoparticles (SiO(2) NPs). Zeta potentials of the SiO(2) NPs and the GAC were measured. Particle size distribution (PSD) of SiO(2) NPs dispersions was analyzed with time to evaluate the extent of aggregation. TEM analysis was conducted. The specific surface area and the pore size distribution of the virgin and the spent GAC were obtained. The fate and transport of the SiO(2) NPs in the GAC fixed bed and their impact on TCE adsorption were found to be a function of their zeta potential, concentration and PSD. The interaction of the SiO(2) NPs and the GAC is of an electrokinetic nature. A weak electrostatic attraction was observed between the SiO(2) NPs and the GAC. This attraction favors SiO(2) NPs attachment on the surface of GAC. SiO(2) NPs attachment onto GAC is manifested by a reduction in the amount of TCE adsorbed during the column breakthrough experiments suggesting a preloading pore blockage phenomenon. However, no effect of SiO(2) NPs was observed on the isotherm and the kinetic studies, this is mainly due to the fast kinetics of TCE adsorption.