Transport and Retention of Zinc Oxide Nanoparticles in Porous Media in the Presence of Naturally Occurring Organic Ligands.

The potential toxicity of nanoscale particles has received considerable attention, but there is little knowledge in the literature relating to the fate and transport of engineered nanoparticles in the environment. In this present study, column experiments were performed to assess the transport and retention of nanoscale zinc oxide particles in saturated quartz sands in the presence of natural organic ligands. Both effluent concentrations and retention profiles were measured over a broad range of physicochemical conditions, which included pH, the presence of a selection of natural organic ligands and an organic buffer. At neutral pHs, ZnO nanoparticles were positively charged and essentially immobile in porous media. The presence of natural organic ligands and a high pH decreased the attachment efficiency facilitating zinc oxide transport through sand columns. Experimental results suggested the presence of both favorable and unfavorable nanoparticle interactions causes significant deviation from classical colloid filtration theory (CFT).