Removal of trichloroethylene by activated carbon in the presence and absence of TiO ₂ nanoparticles

Nanoparticles (NPs) are emerging as a new type of contaminant in water and wastewater. The fate of titanium dioxide nanoparticles (TiO ₂NPs) in a granular activated carbon (GAC) adsorber and their impact on the removal of trichloroethylene (TCE) was investigated. Key parameters governing the TiO ₂NP-GAC interaction such as specific surface area (SSA), zeta potential, and the TiO ₂NP particle size distribution (PSD) were determined. The impact of TiO ₂NPs on TCE adsorption on GAC was tested by conducting TCE adsorption isotherm, kinetic, and column breakthrough studies in the presence and absence of TiO ₂NPs. SSA and pore size distribution of the virgin and spent GAC were obtained. The fate and transport of the TiO ₂NPs in the GAC fixed bed and their impact on TCE adsorption were found to be a function of their zeta potential, concentration, PSD, and the nature of their aggregation. The TiO ₂NPs under investigation are not stable in water and rapidly form larger aggregates. Due to the fast adsorption kinetics of TCE, the isotherm and kinetic studies found no effect from TiO ₂NPs. However, TiO ₂NPs attached to GAC and led to a reduction in the amount of TCE adsorbed during the breakthrough experiments suggesting a preloading pore blockage phenomenon. The analysis of the used GAC confirmed the pore blockage and SSA reduction.