Abstract
Zero-valent iron nanoparticle (nZVI) technology has been found to be promising and effective for the remediation of soils or groundwater. However, while nanoparticles are traveling through porous media, they can rapidly aggregate, causing their settling and deposition. When nZVI are injected in the groundwater flow, the behavior (mobility, dispersion, distribution) is unknown in groundwater, causing the use of enormous quantities of them if used at the field scale. In this paper, a laboratory experiment was carried out with groundwater flow in a two-dimensional, laboratory-scale tank to assess the nanoparticle behavior by means of an image analysis procedure. A solution of zero-valent iron nanoparticles, Nanofer 25S particles, were used and glass beads were utilized as porous medium. The laboratory experiment included the use of a digital camera for the acquisition of the images. The image analysis procedure was used to assess the behavior of nZVI plume. A calibration procedure and a mass balance were applied to validate the proposed image analysis procedure, with the hypothesis that nanoparticles would be uniformly distributed in the third dimension of the tank (thickness). The results show that the nanoparticles presented small dispersive effects and the motion was strongly influenced from the higher weight of them with respect to the water. Therefore, the results indicate that nanoparticles have an own motion not strongly influenced by the fluid flow but more determined from the injection phase and gravity. The statistical elaborations show that the nZVI plume did not respond to the classical mechanisms of the dispersion.
Highlights
Pollution of soil and groundwater is a critical issue worldwide due to improper industrial discharge and waste disposal [1,2]
This paper proposes an image analysis procedure to assess the mobility and dispersion of nanoparticles injected in a saturated porous medium
The image analysis procedure was followed from a processing phase through software and elaborations were finalized to provide information about the distribution, velocity, path, and dispersion of nanoparticles injected in a saturated porous medium and subject to an external fluid motion
Summary
Pollution of soil and groundwater is a critical issue worldwide due to improper industrial discharge and waste disposal [1,2]. Heavy metals and toxic organic compounds are the most common contaminants present in soil and groundwater [1,3,4]. These substances generally hardly degrade and can be found accumulated in soils, they become pollution sources for groundwater [5]. NZVI particles have showed high reactivity to remediate aquifers contaminated by nonaqueous phase liquids, heavy metal ions, and many other hazardous compounds [12,13,14]. NZVI particles are characterized by a large surface area, high reactivity, and possible mobility in the subsurface due to their small size [15]. The surface atoms have a high tendency to interact, adsorb, and react with other atoms or molecules, resulting suitable for remediation actions [17]
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