Mobility of zero valent iron nanoparticles and liposomes in porous media

Suspensions of zero valent iron nanoparticles (nZVI) are commonly used for the in situ remediation of groundwater contaminated with chlorinated solvents. Stable aqueous suspensions of zero-valent nano-particles (nZVI) are prepared by wet chemistry techniques and stabilized with a carboxyl-methyl cellulose (CMC) coating. To enhance their penetration length along with their capacity to attach on oil/water interfaces, nanocomposites are prepared where the CMC-coated nZVI suspension is encapsulated in liposomes. The liposomes might be regarded as vehicles for the safe delivery of nZVI to hydrophobic pollutant targets. The integrity of synthesized liposomes membranes is evaluated with batch tests and flow-through tests in a pre-saturated with oil glass-etched pore network. For assessing the mobility and longevity of nZVI suspensions under flow-through conditions, visualization flow tests are performed on the glass-etched pore network for three types of suspensions: (i) CMC-coated nZVI; (ii) CMC-coated nZVI encapsulated in liposomes; (iii) mixture of CMC-coated nZVI and empty liposomes. The measured iron and lipid concentration breakthrough curves for all cases are interpreted by accounting for the transient changes caused on the particle size distribution in the suspension collected from the outlet. Albeit the CMC-coated nZVI are always very mobile, stable, and detectable in the effluent, a fraction of the liposomes or no liposomes are detected in the effluent, when injecting CMC-coated nZVI encapsulated in liposomes or mixed with empty liposomes, respectively. The flushing of the pore network with water, remobilizes the liposomes and withdraws them completely from the pore system. (C) 2016 Elsevier B.V. All rights reserved.