Transport and Retention of TiO2 Nanoparticles in Saturated Porous Media: Role of Ionic Strength, Valence, and Humic Acid.

The transport and retention behavior of titanium dioxide nanoparticles (needle-like rutile particles with nominal size of 10X40 nm) has been investigated in a saturated porous medium composed of clean quartz sands by injection of stable TiO₂ nanoparticles dispersions. Experiments were carried out under well-controlled solution chemistry conditions, allowing for the sensitivity of nanopartilce transport and retention characteristics to be examined under a range of ionic strength and valence (NaCl vs. CaCl₂), as well as the presence and absence of 5 mg/L Suwannee River humic acid (SRHA).