Pore-scale investigation of the use of reactive nanoparticles for in situ remediation of contaminated groundwater source

Abstract

<jats:p>Nanoscale zero-valent iron (nZVI) particles have excellent capacity for in situ remediation of groundwater resources contaminated by a range of organic and inorganic contaminants. Chlorinated solvents are by far the most treated compounds. Studies at column, pilot, and field scales have reported successful decrease in contaminant concentration upon injection of nZVI suspensions in the contaminated zones. However, the field application is far from optimized, particularly for treatments at—or close to—the source, in the presence of residual nonaqueous liquid (NAPL). The knowledge gaps surrounding the processes that occur within the pores of the sediments hosting those contaminants at microscale limit our ability to design nanoremediation processes that are optimized at larger scales. This contribution provides a pore-scale picture of the nanoremediation process. Our results reveal how the distribution of the trapped contaminant evolves as a result of contaminant degradation and generation of gaseous products. We have used state-of-the-art four-dimensional (4D) imaging (time-resolved three-dimensional [3D]) experiments to understand the details of this degradation reaction at the micrometer scale. This contribution shows that the gas released (from the reduction reaction) remobilizes the trapped contaminant by overcoming the capillary forces. Our results show that the secondary sources of NAPL contaminations can be effectively treated by nZVI, not only by in situ degradation, but also through pore-scale remobilization (induced by the evolved gas phase). The produced gas reduces the water relative permeability to less than 1% and, therefore, significantly limits the extent of plume migration in the short term.</jats:p>

Four-dimensional X-ray micro-tomography imaging of dynamic processes in geosciences

“…The effect of gas injection, i.e., three-phase flow in either immiscible or near-miscible gas conditions has also been assessed [Alhosani et al, 2019]. The techniques can also apply to the in situ remediation of contaminated groundwater by NAPL [Pak et al, 2020]. Multi-phase flow has also been studied in fracture networks and the effects of fracture morphology on the distribution and transport of immiscible fluid phases has been investigated [Karpyn et al, 2007, Van Stappen et al, 2018.…”

Retention of sulfidated nZVI (S-nZVI) in porous media visualized by X-ray μ-CT – the relevance of pore space geometry

“…Pak et al recently used synchrotron based direct μ-CT imaging (voxel size = 3.3 μm) to study trichloroethylene (TCE) degradation by nanoscale zerovalent iron (nZVI) aggregates inside a glass bead pack. 33 However, this study was focused on TCE distribution and did not characterise NP transport behaviour, i.e. , spatial NP retention patterns.…”

Effects of Wettability and Minerals on Residual Oil Distributions Based on Digital Rock and Machine Learning

“…Pore-scale fluid flow experiment is an effective method to investigate the transport mechanisms and distribution characteristics of residual oil, including microfluidics [5][6][7][8], natural sandstone models [9][10][11][12][13], nuclear magnetic resonance [14][15][16], confocal laser [17][18][19], and CT scan [20][21][22]. Owing to the rapid development of CT technology, it has been widely used in EOR [23][24][25][26][27], carbon dioxide storage [28], environmental governance [29], water-rock interaction [30,31], reservoir modelling [32][33][34][35][36], hydraulic conductivity [37,38], and reservoir evaluation [39][40][41][42][43][44][45][46][47]. Due to the advantages of high resolution, nondestructive, and in situ, CT scan has become an effective method for investigating residual oil.…”