Testing the Suitability of Zerovalent Iron Materials for Reactive Walls

Abstract

Environmental ContextGroundwater remediation is mostly a costly long-term process. In-situ remediation by permeable reactive barriers is a potential solution. For pollution by various redox sensitive contaminants, zerovalent iron (ZVI) has been proposed to immobilise or degrade dissolved pollutants in groundwater. Scrap iron materials are considered as an effective low-cost ZVI material. Due to the wide variation of scrap metal compositions, testing methods for characterising the corrosion behaviour need to be developed. AbstractZerovalent iron (ZVI) has been proposed as reactive material in permeable in-situ walls for contaminated groundwater. An economically feasible ZVI reactive wall requires cheap but efficient iron materials. From an uranium treatability study and results of iron dissolution in 0.002 M EDTA by five selected ZVI materials, it is shown that current research and field implementation is not based on a rational selection of application-specific iron metal sources.An experimental procedure is proposed which could enable a better material characterization.This procedure consists in mixing ZVI materials and reactive additives including contaminant 2 releasing materials (CRM) in long term batch experiments and characterise the contaminant concentration over the time.

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“…In other words, the difference in particle size of used materials is minimal (φ value). However, the assertion that 'finer particle size are more reactive than coarser materials' is operationally maintained in this study [11,26,31].…”

“…The fact that materials with finer particle size are more reactive than coarser materials is the rationale for the use of nano-scale particles in water treatment [48,49]. However, it should be recalled that the particle size alone is not an indicator for the intrinsic reactivity [18,31,19]. Rigorously, if the particle size distribution of ZVI9 was not given by the supplier, a researcher could have sieved all three materials and used the fraction 0.40 to 0.80 mm as one fraction.…”

“…1). The presence of atmospheric corrosion products is the main reason why a graphical comparison of materials is not suitable [11,31]. It has been shown that the EDTA test is not suitable for powdered Fe 0 materials and for Fe 0 samples containing a high proportions of fines [11].…”

“…Given the higher stability of Fe III -EDTA relative to Fe II -EDTA, ascorbic acid was identified a powerful agent for the reduction of the Fe III -EDTA prior to Fe determination using the 1,10 orthophenanthroline method [31].…”

“…[Fe] at t = 0, is a reflect of the amount of atmospheric corrosion present at fines at the Fe 0 surface [11,31].…”