A new method to correlate intrinsic reactivity and treatability efficiency of metallic iron ( Metallic iron (Fe 0 ) is a reactive material currently used for environmental remediation and safe drinking water provision [1][2][3][4][5][6][7]. Available Fe 0 materials are obtained from various sources [8][9][10][11][12] and are supposed to satisfy design expectations [7,[13][14][15][16][17]. However, there is no standard method to access the suitability of Fe 0 materials for individual applications. As a rule, used materials are characterized: (i) by selected physical and chemical parameters (e.g.elemental composition, particle size, surface area) and (ii) for their ability to remove the specific species of interest (efficiency in treatability studies) [11,18,19]. However, each reactive material should be primarily characterized by its intrinsic reactivity.The 'intrinsic reactivity' is a material-dependent but system-independent qualitative trend.The 'removal efficiency' or 'treatability efficiency' is a system-dependent quantifiable

The influence of metallic iron (Fe 0 ) amendment on the efficiency of sand to discolor a 2.0 mg L -1 methylene blue (MB) solution was investigated in column studies. MB was used as an indicator to identify the optimum Fe 0 /sand ratio for efficient filtration systems. Columns

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The influence of granular sand on the efficiency of metallic iron (Fe 0) for the discoloration of a methylene blue (MB) solution was investigated in the current work. The initial MB concentration was 10 mg L-1 and mass loadings within the range of 0 to 90 g L-1 for sand and 0 to 45 g L-1 for Fe 0 were applied. The batch reaction vessel used was a graduated essay tube containing 22.0 mL of the MB solution. Shaking intensities of 0 and 75.0 rpm were applied for experimental durations of 7, 21 and 45 days. Results provide clear evidence that both Fe 0 and sand were independently effective for the discoloration of MB. However, the latter material was significantly less effective, recording 54.0 % compared to 82.0 % recorded for the Fe 0 after 45 days in experiment with 45.0 g L-1 of each material. Similarly, mixing 90 g L-1 sand with 45.0 g L-1 of Fe 0 depicted a MB discoloration efficacy of 72.0 % demonstrating that the discoloration capability of the Fe 0 was significantly 'masked' by the presence of sand. This observation provides clear evidence to question the common approach of using adsorbents for contaminant accumulation in the vicinity of Fe 0 materials in order to facilitate chemical reduction by Fe 0. Further research is required to determine the relative affinity of different materials that can be used in Fe 0 mixtures for maximum contaminant removal efficacies.

Humic acid-coated goethite nanoparticles (HA-GoeNPs) have been recently proposed as an effective reagent for the in situ nanoremediation of contaminated aquifers. However, the effective dosage of these particles has been studied only at laboratory scale to date. This study investigates the possibility of using HA-GoeNPs in remediation of real field sites by mimicking the injection and transport of HA-GoeNPs under realistic conditions. To this purpose, a three-dimensional (3D) transport experiment was conducted in a large-scale container representing a heterogeneous unconfined aquifer. Monitoring data, including particle size distribution, total iron (Fetot) content and turbidity measurements, revealed a good subsurface mobility of the HA-GoeNP suspension, especially within the higher permeability zones. A radius of influence of 2 m was achieved, proving that HA-GoeNPs delivery is feasible for aquifer restoration. A flow and transport model of the container was built using the numerical code Micro and Nanoparticle transport Model in 3D geometries (MNM3D) to predict the particle behavior during the experiment. The agreement between modeling and experimental results validated the capability of the model to reproduce the HA-GoeNP transport in a 3D heterogeneous aquifer. Such result confirms MNM3D as a valuable tool to support the design of field-scale applications of goethite-based nanoremediation.