Biomineralization of arsenate to arsenic sulfides is greatly enhanced at mildly acidic conditions

Lucia Rodriguez-Freire, Reyes Sierra-Alvarez, Robert Root, Jon Chorover, James A. Field

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

Arsenic (As) is an important water contaminant due to its high toxicity and widespread occurrence. Arsenic-sulfide minerals (ASM) are formed during microbial reduction of arsenate (AsV) and sulfate (SO42-). The objective of this research is to study the effect of the pH on the removal of As due to the formation of ASM in an iron-poor system. A series of batch experiments was used to study the reduction of SO42- and AsV by an anaerobic biofilm mixed culture in a range of pH conditions (6.1-7.2), using ethanol as the electron donor. Total soluble concentrations and speciation of S and As were monitored. Solid phase speciation of arsenic was characterized by x-ray adsorption spectroscopy (XAS). A marked decrease of the total aqueous concentrations of As and S was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The amount of As removed was 2-fold higher and the rate of the As removal was up to 17-fold greater at pH 6.1 than at pH 7.2. Stoichiometric analysis and XAS results confirmed the precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results taken as a whole suggest that ASM formation is greatly enhanced at mildly acidic pH conditions.

Original languageEnglish (US)
Pages (from-to)242-253
Number of pages12
JournalWater research
Volume66
DOIs
StatePublished - Dec 1 2014

Keywords

  • Arsenate reduction
  • Biomineralization
  • Bioprecipitation
  • Orpiment
  • Realgar
  • Sulfate reduction

ASJC Scopus subject areas

  • Ecological Modeling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

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