Thermodynamic controls on the kinetics of microbial low-pH Fe(II) oxidation

Lance N. Larson, Javier Sánchez-España, Bradley Kaley, Yizhi Sheng, Kyle Bibby, William D. Burgos

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Acid mine drainage (AMD) is a major worldwide environmental threat to surface and groundwater quality. Microbial low-pH Fe(II) oxidation could be exploited for cost-effective AMD treatment; however, its use is limited because of uncertainties associated with its rate and ability to remove Fe from solution. We developed a thermodynamic-based framework to evaluate the kinetics of low-pH Fe(II) oxidation. We measured the kinetics of low-pH Fe(II) oxidation at five sites in the Appalachian Coal Basin in the US and three sites in the Iberian Pyrite Belt in Spain and found that the fastest rates of Fe(II) oxidation occurred at the sites with the lowest pH values. Thermodynamic calculations showed that the Gibbs free energy of Fe(II) oxidation (ΔGoxidation) was also most negative at the sites with the lowest pH values. We then conducted two series of microbial Fe(II) oxidation experiments in laboratory-scale chemostatic bioreactors operated through a series of pH values (2.1-4.2) and found the same relationships between Fe(II) oxidation kinetics, ΔGoxidation, and pH. Conditions that favored the fastest rates of Fe(II) oxidation coincided with higher Fe(III) solubility. The solubility of Fe(III) minerals, thus plays an important role on Fe(II) oxidation kinetics. Methods to incorporate microbial low-pH Fe(II) oxidation into active and passive AMD treatment systems are discussed in the context of these findings. This study presents a simplified model that describes the relationship between free energy and microbial kinetics and should be broadly applicable to many biogeochemical systems.

Original languageEnglish (US)
Pages (from-to)9246-9254
Number of pages9
JournalEnvironmental Science and Technology
Volume48
Issue number16
DOIs
StatePublished - Aug 19 2014

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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