Application of an empirical transport model to simulate retention of nanocrystalline titanium dioxide in sand columns

Transport and retention behaviors of titanium dioxide nanoparticles in iron oxide-coated quartz sand: Effects of pH, ionic strength, and humic acid

“…Moreover, in contrast with the similar retained profiles in iron oxide-coated sand observed across the entire ionic strength range examined without SRHA at both pH conditions, the non-monotonic retained profiles observed with SRHA at both pH conditions were sensitive to solution ionic strength, as indicated by the maximum retained concentrations at locations more downgradient of the inlet at 1 mM ionic strength relative to those at 10 mM ionic strength in NaCl solution. Although a non-monotonic retained profile of nTiO 2 has also been reported in previous studies [15,19,23], to the best of our knowledge, there have been no observations concerning non-monotonic retained profiles of colloids and nanoparticles obtained in iron or aluminum mineral-coated sands.…”

“…Samples from the column effluent were collected at 20-min intervals in 15-mL sterile centrifuge tubes. The influent and effluent concentrations of nTiO 2 were analyzed via inductively coupled plasma atomic emission spectroscopy (ICP-AES) after heating in a digestion device with 5 mL of concentrated H 2 SO 4 and 2 g of (NH 4 ) 2 SO 4 at 200 • C for more than 2 h [15,51]. The pore water velocity of all experiments was set to be 4 m day −1 (0.38 mL min −1 ) to represent fluid velocities in coarse aquifer sediments, forced-gradient conditions, or engineered filtration systems [52].…”

“…Previous studies also revealed that nTiO 2 could facilitate the transport of coexisting pollutants in the natural environment due to the adsorption of the environmental contaminants onto nTiO 2 surfaces [10,11]. Hence, a great number of studies investigated the fate and transport of nTiO 2 in soils and groundwater [2,4,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

“…Physical, chemical, and biological factors such as fluid velocity [13][14][15][16], solution chemistry (pH, ionic strength, and ion valence) [2,4,14,[17][18][19], nanoparticle concentration [14,15], surfactant and polymer coating [16,18,20], natural organic matter [21][22][23][24][25][26], bacteria [24], biofilm [27], and the co-presence of other nanoparticles [28] have been found to affect the transport and deposition kinetics of nTiO 2 . Most of these previous studies were performed in model porous media (i.e.…”

Characterization of nanoparticle transport through quartz and dolomite gravels by magnetic resonance imaging

“…In this approach, the concentration of nanoparticles eluting from the column outflow is monitored. Colloid filtration theory (and its variants) is then used to interpret the breakthrough curves and thus provide constants for predictive transport models (Choy et al 2008;Tiraferri and Sethi 2009). While highly informative, the data obtained are a bulk average of a complex and heterogeneous array of interactions within the column.…”