Standardization of the reducing power of zero-valent iron using iodine

Abstract

Because iron-based materials that are used for the permeable reactive barrier systems come in various shapes, sizes, and with various surface properties depending on the manufacturing sources, their reductive powers vary in a wide spectrum. A new experimental procedure to evaluate the reductive power of iron material was developed in this study. Tri-iodide (I3(-)) was used as the representative oxidizing agent that reacts with zero-valent iron (ZVI). Three iron-based materials (two scraps, two powders) and four chlorinated chemicals [perchloroethene (PCE), trichloroethene (TCE), 1,1,1-trichloroethane (TCA), and pentachlorophenol (PCP)] were used in this study. Redox reactions were conducted in glass vials containing aqueous solutions of chlorinated compounds or tri-iodide with known masses of iron material. After a predetermined reaction time each vial was opened and the solution was analyzed for the concentration of reduced compound. The apparent rate contant (k(i)(obs)) of iodine reduction reaction with ZVIs was found to be proportional to that (k(c)(obs)) of chlorinated contaminant. The surface area-normalized reduction rate constants (k(c)(nor)) for contaminants and tri-iodide (k(i)(nor)) were also proportional to each other. The ratio of rate constants, K(nor) (= k(c)(nor)/k(i)(nor)) was estimated for each contaminant; 3.29 × 10(-7), 5.86 × 10(-7), 6.70 × 10(-7), and 7.87 × 10(-10) M, for PCE, TCE, TCA, and PCP, respectively. The results of this study suggest that the reductive power of ZVI materials can be standardized using tri-iodide, and thus, can provide a good reference for the quantitative assessment of the reactivity of metallic reducing agents of environmental interest including ZVIs.

Making Fe0-Based Filters a Universal Solution for Safe Drinking Water Provision

“…However, this result is only qualitative as different iron nails would show different results and there is no tool to correlate the obtained results to those of Smith et al [229]. During the last 20 years, sporadic efforts to characterize the intrinsic reactivity of Fe 0 materials have been presented [83,84,90,91,93,94,115,116,224]. However, only the methods of Reardon [90] (H 2 evolution) and Noubactep (Fe 0 dissolution in EDTA) [84] are really simple and affordable.…”

“…However, advice and knowledge transfer can be acquired in collaboration with other groups, including scientific ones. Considering the significant advancements made in research on 'Fe 0 for environmental remediation and water treatment' over the past three decades [26][27][28][29][30]52,76,116,146,[222][223][224][225][226][227][228][229] as the cornerstone for a universal sustainable solution to a long-lasting crisis, the universal provision of safe drinking water is no longer an 'elusive goal' [7]; Fe 0 filtration provides a solution, specifically for the developing world [229,230].…”

The Impact of Selected Pretreatment Procedures on Iron Dissolution from Metallic Iron Specimens Used in Water Treatment

“…For the materials tested herein, it can be postulated that there are situations in which SW is suitable and others where GI1, GI2 or GI3 are better suitable. The long history of using Fe 0 for water treatment suggests that suitable Fe 0 materials were mostly found for reported success stories, but the rational for their selection has not been really realized [58,63,64]. Even today, it is current to consider GI or SW as a class of material compared to nano-Fe 0 , iron nails or bimetallics.…”

“…A key reason for this is the large variability of experimental conditions used in testing Fe 0 materials [58][59][60][61][62]. The main influencing operational parameter seems to be Fe 0 itself [58,61,63,64]. In fact, data from the open corrosion literature demonstrate that at pH > 4.5, the extent of iron corrosion depends on the relative kinetics of iron oxidative dissolution (corrosion) and of the precipitation of resulting iron hydroxides and oxides (oxide-scale formation) [65][66][67][68][69].…”

Stabilization of Iron (Micro)Particles with Polyhydroxybutyrate for In Situ Remediation Applications

“…Different methods have been proposed to provide a good reference for the quantitative assessment of the reactivity of metallic reducing agents of environmental interest, including ZVIs. The most relevant examples include the use of concentrated Fe(III) solution [16], tri-iodide [17], and methylene blue [18].…”