The Mineralogic Transformation of Ferrihydrite Induced by Heterogeneous Reaction with Bioreduced Anthraquinone Disulfonate (AQDS) and the Role of Phosphate

Journal Article · Wed Oct 12 04:00:00 EDT 2011 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/j.gca.2011.06.030· OSTI ID:1029083

Zachara, John M; Kukkadapu, Ravi K; Peretyazhko, Tetyana; Bowden, Mark E; Wang, Chong M; Kennedy, David W; Moore, Dean A; Arey, Bruce W

Anthraquinone-2-6-disulfonate (AQDS) enhances electron donor utilization and mineral product crystallization in studies of Fe(III) oxide reductive mineralization by metal reducing bacteria (MRB) through heterogeneous redox reaction. In spite of the strong effect of AQDS in these systems, little information exits on its direct role in reductive mineralization. To provide such insights, bioreduced AQDS (AH2DS; dihydro-anthraquinone) was reacted with a 2-line, Si-substituted ferrihydrite under anoxic conditions at neutral pH in PIPES buffer. Phosphate (P) and bicarbonate (C); common adsorptive oxyanions and media/buffer components known to effect ferrihydrite mineralization; and Fe(II)aq (as a catalytic mineralization agent) were used in comparative experiments. Heterogeneous AH2DS oxidation coupled with Fe(III) reduction occurred within 0.13-1 day, with mineralogic transformation occurring thereafter. The product suite included lepidocrocite, goethite, and/or magnetite, with proportions varing with reductant:oxidant ratio (r:o) and the presence of P or C. Lepidocrocite was the primary product at low r:o in the absence of P or C, with evidence for multiple formation pathways. P inhibited reductive recrystallization, while C promoted goethite formation. Stoichiometric magnetite was the sole product at higher r:o in the absence and presence of P. Lepidocrocite was the primary mineralization product in the Fe(II)aq system, with magnetite observed at near equal amounts when Fe(II) was high [Fe(II)/Fe(III)]=0.5 and P was absent. P had a greater effect on reductive mineralization in the Fe(II)aq system, while AQDS was more effective than Fe(II)aq in promoting magnetite formation. The direct AH2DS-driven reductive reaction pathway produced mineral products that were different from AH2DS-ferrihydite-MRB systems, particularly in presence of P.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1029083
• Report Number(s): PNNL-SA-76025; 4593; KC0303020
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 21 Vol. 75; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ACID CARBONATES
ANTHRAQUINONES
AQDS
BACTERIA
BINDING ENERGY
CRYSTALLIZATION
ELECTRONS
Environmental Molecular Sciences Laboratory
GOETHITE
MAGNETITE
MINERALIZATION
OXIDATION
OXIDES
PHOSPHATES
RECRYSTALLIZATION
REDOX REACTIONS
TRANSFORMATIONS
VALENCE
ferrihydrite
phosphate