The Implications of Fe_2O_3 and TiO_2 Nanoparticles on the Removal of Trichloroethylene by Activated Carbon in the Presence and Absence of Humic Acid

摘要

The impact of Fe_2O_3 and TiO_2 nanoparticles (NPs) on the removal of trichloroethylene (TCE) in a granular activated carbon (GAC)-fixed bed adsorber was investigated in the presence of humic acid (HA). The surface charges of GAC and NPs were obtained in the presence and absence of HA with the NPs behaving similarly. Isotherm and column studies were conducted in the presence and absence of the NPs and HA. NPs had no effect on TCE adsorption during isotherm studies. However, in the column studies conducted with organic-free water, the presence of NPs resulted in a reduction in TCE capacity most likely due to pore blockage by aggregating NPs. This effect was completely mitigated in the presence of HAs that prevented an association between the GAC and the NPs, and between NPs. The presence of HA provided a high negative charge on the GAC and on the nanoparticles resulting in repulsive forces between the GAC and the NPs, and between NPs, thereby preventing pore blockage. Both Fe_2O_3 and TiO_2 NPs demonstrated that charge characteristics are more important than chemical characteristics. Pore-size distribution of the fresh and the spent GAC confirmed the adsorption data but points to some HA and NP interaction with the carbon.