The effects of surface aging on nanoparticle fate and transport in natural and engineered porous media.
Nanomaterials will be subjected to various surface transformations in the environment
and within water and wastewater treatment systems. A comprehensive understanding of the
fate and transport behavior of "aged" nanomaterials in both natural and engineered
porous media is required in order to accurately quantify ecological and human health
risks. This research sought to (1) evaluate... read morethe impact of ultraviolet (UV) light aging
on nanoparticle transport in water-saturated porous media; and (2) assess the effects of
influent water quality on silver nanoparticle retention and dissolution in ceramic water
filters. Additionally, the value of quartz crystal microbalance (QCM-D) data in
nanoparticle fate and transport studies was evaluated by comparing deposition behavior
in complementary QCM-D and sand columns experiments. Silver (nAg) and iron oxide
nanoparticles exposed to UV light were up to 50% more strongly retained in porous media
compared with freshly prepared suspensions due to less negative surface charge and
larger aggregate sizes. UV-aged nAg were more prone to dissolution in sand columns,
resulting in effluent Ag+ concentrations as high as 1.2 mg/L. In ceramic water filters,
dissolution and cation exchange processes controlled silver release into treated water.
The use of acidic, high salinity, or high hardness water accelerated oxidative
dissolution of the silver coating and resulted in effluent silver concentrations 5-10
times above international drinking water guidelines. Results support the recommendation
for a regular filter replacement or silver re-application schedule to ensure ongoing
efficacy. Taken in concert, these research findings suggest that oxidative aging of
nanomaterial surfaces (either through exposure to UV light or aggressive water
chemistries) will alter the fate of nanomaterials in the environment and may decrease
the effective lifetime of devices which utilize nanotechnology. Corresponding QCM-D and
column experiments revealed that nanoparticles were generally more mobile in QCM-D due
to reduced diffusive transport of larger aggregates to the sensor surface and high
primary energy barriers to deposition. While QCM-D may be used to provide qualitative
data, direct comparisons of deposition rates in QCM-D with attachment rates obtained
from column experiments may prove difficult due to differences in flow geometry and
surface characteristics between the two
Thesis (Ph.D.)--Tufts University, 2015.
Submitted to the Dept. of Civil Engineering.
Advisor: Kurt Pennell.
Committee: Linda Abriola, John Fortner, Daniele Lantagne, and Douglas Matson.
Keywords: Environmental engineering, and Nanotechnology.read less