Understanding abiotic ferrihydrite re-mineralization by ferrous ions

Research output: Contribution to journalArticle

Abstract

In this work, we study the abiotic re-mineralization of ferrihydrite under reducing conditions, obtained by adding zero-valent iron (ZVI) to a suspension of ferrihydrite particles. Under similar conditions, the system (ferrihydrite and ZVI) proceeded along two different transformation pathways differentiated by whether a magnetic stirrer or an overhead stirrer was used for mixing. X-ray diffraction characterization of the solid products showed that magnetite was the sole product of ferrihydrite transformation when a magnetic stirrer was used, whereas both goethite and magnetite were formed when an overhead stirrer was used. The system also behaved differently in terms of transformation kinetics and amount of magnetite formed. The quantification of magnetite generated was performed using a procedure developed in this study. The role of four mechanisms was investigated to explain these observed differences, namely—(1) presence/absence of high local Fe<sup>2+</sup> concentrations, (2) mechanical abrasion, (3) presence/absence of a magnetic field, and (4) presence/absence of a crystalline ZVI surface. Ferrous ions are expected to be concentrated near the magnetic bead on the magnetic stirrer as opposed to a more dispersed distribution with the overhead stirrer. This mechanistic study concluded that the presence of high local Fe<sup>2+</sup> concentrations in the system leads to magnetite formation and the absence of the same leads to mixed goethite/magnetite or magnetite-free systems. These findings have significant implications for the mobilization of arsenic from iron (III) hydroxides as the conditions move from oxidizing to reducing, such as often occurs in engineered landfills and natural carbon-rich sediments.

Original languageEnglish (US)
Pages (from-to)1945-1956
Number of pages12
JournalInternational Journal of Environmental Science and Technology
Volume12
Issue number6
DOIs
StatePublished - Jun 1 2015

Fingerprint

Ferrosoferric Oxide
ferrihydrite
magnetite
remineralization
Magnetite
mixers
mineralization
Ions
ions
iron
ion
Iron
goethite
Waste Disposal Facilities
hydroxides
landfills
Arsenic
Magnetic Fields
magnetic fields
abrasion

Keywords

  • Arsenic
  • Iron compounds
  • Landfills
  • Phase transformation
  • Water treatment

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Environmental Chemistry
  • Environmental Engineering

Cite this

Understanding abiotic ferrihydrite re-mineralization by ferrous ions. / Raghav, M.; Saez, Avelino E; Ela, Wendell P.

In: International Journal of Environmental Science and Technology, Vol. 12, No. 6, 01.06.2015, p. 1945-1956.

Research output: Contribution to journalArticle

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