Kinetics of Reductive Dissolution of Hematite by Bioreduced Anthraquinone-2,6-disulfate

Journal Article · Thu Nov 15 04:00:00 EST 2007 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es070768k· OSTI ID:921826

Liu, Chongxuan; Zachara, John M; Foster, Nancy S; Strickland, Janae

The reductive dissolution of hematite (α-Fe₂O₃) was investigated in a flow-through system using AH₂DS, a reduced form of anthraquinone- 2,6 disulfonate (AQDS), which is often used as an electron shuttling compound in studies of dissimilatory microbial reduction of iron oxides. Influent flow-rate, pH, Fe(II) and phosphate concentrations were varied to investigate the redox reaction kinetics. The effluent AH₂DS, AQDS, and Fe(II) concentrations changed significantly within the first half hour of AH₂DS reaction with hematite and then gradually evolved toward steady-state. The steady-state rates decreased with increasing pH from 4.5 to 7.6 and decreased with decreasing flow-rate. The rates also decreased with increasing influent concentration of Fe(II) or phosphate that formed surface complexes at the experimental pH. Mineral surface properties, Fe(II) complexation reactions, and AQDS sorption on hematite surfaces were independently investigated for interpreting hematite reductive dissolution kinetics. AH₂DS sorption to hematite was inferred from the parallel measurements of AQDS and AH₂DS sorption to α-Al₂O₃, a redox stable analog of α-Fe₂O₃. Decreasing Fe(II) and increasing AH₂DS sorption by controlling flow residence time, influent pH, Fe(II) and phosphate concentrations increased the rates of reductive dissolution. The rates were also affected by the redox reaction free energy when reductive dissolution approached equilibrium, as shown by the effect of increasing the influent concentration of Fe(II).

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 921826
• Report Number(s): PNNL-SA-54233; KC0303020
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 22 Vol. 41; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
ANTHRAQUINONES
AQDS
hematite
iron oxides
reduction
dissolution
BIODEGRADATION
CHEMICAL REACTION KINETICS
DISSOLUTION
HEMATITE
REDOX REACTIONS
REDUCTION
SULFONATES