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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

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

Authors: Rodriguez-Freire, Lucia; Sierra-Alvarez, Reyes; Root, Robert; Chorover, Jon; Field, James A

Published In Water Res, (2014 Dec 01)

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 (As(V)) and sulfate (SO4(2-)). 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 SO4(2-) and As(V) 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.

PubMed ID: 25222328 Exiting the NIEHS site

MeSH Terms: Adsorption; Arsenates/chemistry*; Arsenic/chemistry*; Arsenicals/chemistry*; Bacteria/metabolism; Biodegradation, Environmental; Bioreactors; Electrons; Hydrogen-Ion Concentration; Minerals/chemistry; Sulfates/chemistry; Sulfides/chemistry*; Water; Water Pollutants, Chemical/analysis; Water Purification/methods*

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