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

WATER RESEARCH

卷:66

Article

Rodriguez-Freire, Lucia¹  Sierra-Alvarez, Reyes¹  Root, Robert²  Chorover, Jon²  Field, James A.¹ 

[1] Univ Arizona, Dept Chem & Environm Engn, Tucson, AZ 85721 USA

[2] Univ Arizona, Dept Soil Water & Environm Sci, Tucson, AZ USA

关键词: Arsenate reduction;    Sulfate reduction;    Bioprecipitation;    Orpiment;    Realgar;    Biomineralization;   

DOI  :  10.1016/j.watres.2014.08.016

来源: Elsevier

【 摘 要 】

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 (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 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. (C) 2014 Elsevier Ltd. All rights reserved.

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