Arsenic Repartitioning during Biogenic Sulfidization and Transformation of Ferrihydrite

Journal Article · Fri Jan 01 04:00:00 EST 2010 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/j.gca.2009.10.023· OSTI ID:1019756

Kocar, B; Borch, T; Fendorf, S

Iron (hydr)oxides are strong sorbents of arsenic (As) that undergo reductive dissolution and transformation upon reaction with dissolved sulfide. Here we examine the transformation and dissolution of As-bearing ferrihydrite and subsequent As repartitioning amongst secondary phases during biotic sulfate reduction. Columns initially containing As(V)-ferrihydrite coated sand, inoculated with the sulfate reducing bacteria Desulfovibrio vulgaris (Hildenborough), were eluted with artificial groundwater containing sulfate and lactate. Rapid and consistent sulfate reduction coupled with lactate oxidation is observed at low As(V) loading (10% of the adsorption maximum). The dominant Fe solid phase transformation products at low As loading include amorphous FeS within the zone of sulfate reduction (near the inlet of the column) and magnetite downstream where Fe(II){sub (aq)} concentrations increase; As is displaced from the zone of sulfidogenesis and Fe(III){sub (s)} depletion. At high As(V) loading (50% of the adsorption maximum), sulfate reduction and lactate oxidation are initially slow but gradually increase over time, and all As(V) is reduced to As(III) by the end of experimentation. With the higher As loading, green rust(s), as opposed to magnetite, is a dominant Fe solid phase product. Independent of loading, As is strongly associated with magnetite and residual ferrihydrite, while being excluded from green rust and iron sulfide. Our observations illustrate that sulfidogenesis occurring in proximity with Fe (hydr)oxides induce Fe solid phase transformation and changes in As partitioning; formation of As sulfide minerals, in particular, is inhibited by reactive Fe(III) or Fe(II) either through sulfide oxidation or complexation.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: DOE - OFFICE OF SCIENCE
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1019756
• Report Number(s): BNL--95602-2011-JA
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 3 Vol. 74; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ADSORPTION
ARSENIC
DESULFOVIBRIO
DISSOLUTION
IRON
IRON SULFIDES
LACTATES
MAGNETITE
OXIDATION
PHASE TRANSFORMATIONS
SAND
SULFATE-REDUCING BACTERIA
SULFATES
SULFIDE MINERALS
SULFIDES
TRANSFORMATIONS
national synchrotron light source