Characterizing the effects of shaking intensity on the kinetics of metallic iron dissolution in EDTA

Abstract

Despite two decades of intensive laboratory investigations, several aspects of contaminant removal from aqueous solutions by elemental iron materials (e.g., in Fe(0)/H2O systems) are not really understood. One of the main reasons for this is the lack of a unified procedure for conducting batch removal experiments. This study gives a qualitative and semi-quantitative characterization of the effect of the mixing intensity on the oxidative dissolution of iron from two Fe(0)-materials (materials A and B) in a diluted aqueous ethylenediaminetetraacetic solution (2 mM EDTA). Material A (fillings) was a scrap iron and material B (spherical) a commercial material. The Fe(0)/H2O/EDTA systems were shaken on a rotational shaker at shaking intensities between 0 and 250 min(-1) and the time dependence evolution of the iron concentration was recorded. The systems were characterized by the initial iron dissolution rate (k(EDTA)). The results showed an increased rate of iron dissolution with increasing shaking intensity for both materials. The increased corrosion through shaking was also evidenced through the characterization of the effects of pre-shaking time on k(EDTA) from material A. Altogether, the results disprove the popular assumption that mixing batch experiments is a tool to limit or eliminate diffusion as dominant transport process of contaminant to the Fe(0) surface.

Metallic Iron Filters for Universal Access to Safe Drinking Water

“…In using activated carbon for wastewater treatment, for example, it is generally accepted that a good decolorizing carbon should fulfill at least 200 mg/g removal capacity for methylene blue in batch experiments [66]. Until recently, there was no experimental parameter to characterize the intrinsic reactivity of Fe 0 materials [67][68][69]. Noubactep [68,69] introduced a parameter, kEDTA, which could enable purposeful material selection.…”

“…Until recently, there was no experimental parameter to characterize the intrinsic reactivity of Fe 0 materials [67][68][69]. Noubactep [68,69] introduced a parameter, kEDTA, which could enable purposeful material selection. kEDTA is the slope of the line of the time dependent oxidative dissolution of ions from a given Fe 0 material in a 2 mM EDTA solution.…”

Characterizing the reactivity of metallic iron in Fe0/EDTA/H2O systems with column experiments

“…Efforts to characterize electrochemical reactivity of Fe 0 in neutral and close-to-neutral solutions are complicated by two major parameters: (i) the formation of oxide layers on Fe 0 , and (ii) the interactions of dissolved species within the oxide layers. Therefore, efforts has been made to characterize iron-corrosion-related processes in the absence of oxide layers [15,26,30,31].…”

“…Based on previous works, a working EDTA-solution of 0.002 M was used [15,31,32]. acid sodium salt were of analytical grade.…”

Arsenate removal from water using Fe3O4-loaded activated carbon prepared from waste biomass

“…Among these technologies, the use of Fe 0 for As removal and remediation has attracted increasing attention due to its effectiveness and applicability under different geochemical conditions, operational simplicity and low-cost [2,3,6]. Critical reviews and indepth investigations of Fe 0 for environmental remediation have been made by Noubactep et al [7][8][9][10][11]. In field applications, permeable reactive barriers (PRBs) were installed through placement of Fe 0 as a reactive material for immobilization and removal of multiple contaminants including halogenated organic solvents, heavy metals, radionuclides and As [3,12,13].…”