A Non-dimensional Analysis of Permeability Loss in Zero-Valent Iron Permeable Reactive Barrier (PRB)

Abstract

Zero-valent iron (ZVI) permeable reactive barrier (PRB) is a treatment wall filled with ZVI as a reactive material that is installed perpendicular to the groundwater flow in the subsurface. To aid design of these PRBs, a non-dimensional analysis of the permeability reduction has been carried out in this work where the dimensionless equation has been identified to correlate different variables. Additionally, the change in physical features of ZVI PRB has been identified using the inspection system of x-ray microcomputer tomography (µCT) and it has shown that the particle size is expanding, thus reducing the permeability. The change in chemical composition that impact the surface reactivity has been confirmed using x-ray diffraction (XRD) and the corroded products of maghemite and magnetite have been identified. Flow experiments have been conducted to observe and measure the changes in permeability, where the pressure at various points of the experimental rigs has been measured for the calculation of permeability values. The reduction in permeability could be observed from both small and large scale experiments. For example, the flow experiments indicated that the permeability value has been significantly reduced for coarse particle, e.g., in small scale experiment, it reduced from 7.04E-8 to 3.09E-9 cm 2. It can also be seen that the permeability is decreased by 95.6% for small scale (coarse particle) and by 79.5% for large scale.

Characterizing a Newly Designed Steel-Wool-Based Household Filter for Safe Drinking Water Provision: Hydraulic Conductivity and Efficiency for Pathogen Removal

“…The results of experiment 1 depict the typical profile of permeability loss in Fe 0 -based filtration systems [17,49] with the φ value dropping very abruptly. This behavior has been attributed to a local formation of a cake within the filter [50]. Clearly the system stays still mostly porous, but the inter-connectivity is suppressed in a domain where cake is formed.…”

Redirecting Research on Fe0 for Environmental Remediation: The Search for Synergy

“…The mean feature of the reasoning based on Equation (6) is that modeling porosity loss should have started by considering pore filling by expansive FeCPs [42]. Pore filling by the process of iron corrosion has only recently been demonstrated by X-ray computed tomography of systems containing Fe 0 and deionized water [48,53]. Again, with a proper system analysis, this evidence would have been considered in the early phase of the technology development.…”

“…Again, with a proper system analysis, this evidence would have been considered in the early phase of the technology development. Instead, it is still under discussion whether mixing Fe 0 with non-expansive aggregates (e.g., gravel, pumice, sand) is suitable for efficient systems [48,53].…”

Realizing the potential of metallic iron for environmental remediation: Flee or adapt?

“…It may be surprizing to read that investigating the contribution of expansive iron corrosion to the process of permeability loss in Fe 0 PRBs is an innovation. This becomes obvious, however, when it is recognized that no single contaminant can oxidize Fe 0 , while current models for predicting the operation of Fe 0 PRBs are mostly based on the stoichiometry of an electrochemical reaction between Fe 0 and the contaminants of concern [25,26]. Thus, such models are premised on the wrong scienti c principle.…”