Facilitated transport of anatase titanium dioxides nanoparticles in the presence of phosphate in saturated sands

Soil and water environments are inevitably contaminated by the excess of artificial nanoparticles (NPs) and phosphorus (P) fertilizers. There is a possibility of phosphate facilitating or inhibiting the transport of nanoparticles titanium dioxides (nTiO(2)). It is a great urgency and high priority to investigate the nTiO(2) retention mechanisms and accurately describe the transport of nTiO(2) in the presence of phosphate. Anatase nTiO(2) with two sizes of 20 and 50 nm through the saturated porous sand columns were observed under the conditions (0-50 mM NaNO3 electrolyte, influent P concentrations of 0.10 mM and 2.0 mM, pH 6.5 and 7.5). The experimental results show the phosphate favor the dispersion of nTiO(2), and consequently improve their transport patterns. The likely mechanism is that phosphate adsorption increasing the negative charge on the surface promotes the transportability of nTiO(2) resulting from the low deposition rate and attachment efficiency of NPs. In particular, the facilitated transport of nTiO(2) (50 nm) is greater than those relative smaller as 20 nm. In addition, this enhancement of nTiO(2) transportability by phosphate at pH 6.5 is increased at higher pH of 7.5 due to the more negative zeta potential of surface, which indicates the potential risks to groundwater systems. (C) 2015 Elsevier Inc. All rights reserved.