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

Lookup NU author(s): Dr Lucia Rodriguez Freire


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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.

Publication metadata

Author(s): Rodriguez-Freire L, Sierra-Alvarez R, Root R, Chorover J, Field JA

Publication type: Article

Publication status: Published

Journal: Water Research

Year: 2014

Volume: 66

Pages: 242-253

Print publication date: 01/12/2014

Online publication date: 24/08/2014

Acceptance date: 14/08/2014

ISSN (print): 0043-1354

ISSN (electronic): 1879-2448

Publisher: Elsevier Ltd


DOI: 10.1016/j.watres.2014.08.016


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