Abstract
AbstractMagnetic resonance imaging (MRI) has tremendous potential for revealing transport processes in engineered and geologic systems. Here, we utilize MRI to image nanoparticle (NP) transport through a saturated coarse-grained system. Commercially available paramagnetically tagged NPs are used; the paramagnetic tag making the NP visible to MRI. NP transport was imaged as NPs migrated through packed columns of quartz and dolomite gravel. Changes in T2-weighted image intensity were calibrated to provide fully quantitative maps of NP concentration at regular time intervals (T2being the spin–spin relaxation time of1H nuclei). Transport of nanoparticles was significantly retarded in dolomite compared to quartz due to electrostatic attraction between nanoparticle and dolomite surfaces. NP concentration profiles were evaluated with the CXTFIT computer package to estimate nanoparticle transport parameters at multiple points along the length of the column. This provided temporally resolved parameters that standard breakthrough curve analysis cannot provide. Particle–surface interaction energy profiles were described through Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. While dispersion coefficients and fast deposition rate constant (kfast) were found to increase with distance, deposition rate constant (k) and collision efficiency (α) were found to decrease with distance. These length-dependant variations have significant scaling-up implications for transport models used to predict NP transport in natural and engineered coarse-grained systems, such as sustainable urban drainage systems and river beds.
Highlights
While the advantages afforded by nanotechnology are considerable and diverse, ecotoxicological studies have demonstrated that exposure of aquatic organisms to some nanoparticles can produce deleterious effects
While in a previous study, we utilized Magnetic resonance imaging (MRI) to examine the transport of two different nanomagnetitebased nanoparticles through quartz gravel (Ramanan et al 2012), here we report on the transport of a single type of gadolinium-based NP through two different gravel types
The results reported here indicated that key transport parameters such as dispersivity and the collision efficiency varied along the length of the column
Summary
While the advantages afforded by nanotechnology are considerable and diverse, ecotoxicological studies have demonstrated that exposure of aquatic organisms to some nanoparticles can produce deleterious effects. MR imaging can be used to collect high spatial resolution images of colloid and NP transport inside packed columns in two and three dimensions, when paramagnetically labelled particles are used (Baumann and Werth 2005; Ramanan et al 2012). This technology works not by imaging the paramagnetic particle itself, but by imaging its effect on the H nuclei of surrounding water molecules. The transport of nanoparticles (50 nm in diameter) through packed columns of natural media (quartz and dolomite gravel) was imaged by MRI. This study was carried out from 2009 to 2011 at the School of Geographical and Earth Sciences and GEMRIC, University of Glasgow, Glasgow, UK
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
