Abstract
AbstractOver the past 30 years the literature has burgeoned with in situ approaches for groundwater remediation. Of the methods currently available, the use of metallic iron (Fe0) in permeable reactive barrier (PRB) systems is one of the most commonly applied. Despite such interest, an increasing amount of experimental and field observations have reported inconsistent Fe0 barrier operation compared to contemporary theory. In the current work, a critical review of the physical chemistry of aqueous Fe0 corrosion in porous media is presented. Subsequent implications for the design of Fe0 filtration systems are modeled. The results suggest that: (i) for the pH range of natural waters (>4.5), the high volumetric expansion of Fe0 during oxidation and precipitation dictates that Fe0 should be mixed with a non‐expansive material; (ii) naturally occurring solute precipitates have a negligible impact on permeability loss compared to Fe0 expansive corrosion; and (iii) the proliferation of H2 metabolizing bacteria may contribute to alleviate permeability loss. As a consequence, it is suggested that more emphasis must be placed on future work with regard to considering the Fe0 PRB system as a physical (size‐exclusion) water filter device.
Highlights
Over the past 30 years the literature has burgeoned with in-situ approaches for groundwater remediation
Some available experimental results from batch [15,16] and column [14,17] studies suggest that admixing pumice/sand to Fe0 is beneficial for the process of contaminant removal
At present it is suggested that the mechanism of permeability loss in Fe0 permeable reactive barrier (PRB) is due to the Introduction accumulation of insoluble minerals within the PRB pore network [10,13]
Summary
Fe0 particles have been widely reported as successful for water treatment [50,51,52,53]. These include conventional slow sand filters (SSF), biosand filters (BSF) and iron oxidecoated sand filters. The reproducibility and comparison of reported results from one setting to another is problematic To fill this gap, Kubare and Haarhoff [41] have provided the most recent systematic review for a rational design of BSF. A Fe0 filtration system (Fig. 2) can be regarded as a modification of a SSF or BSF (point O). It is essential to carefully develop rational and comprehensive engineering design criteria In this effort, designing tools for BSF would be very helpful [41,55]
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