Micromodel Investigation of Transport Effect on the Kinetics of Reductive Dissolution of Hematite

Journal Article · Wed Mar 13 04:00:00 EDT 2013 · Environmental Science & Technology, 47(9):4131-4139

DOI:https://doi.org/10.1021/es304006w· OSTI ID:1086412

Zhang, Changyong; Liu, Chongxuan; Shi, Zhi

Reductive dissolution of hematite in porous media was investigated using a micromodel with realistic pore network structures that include distinctive advection domain, macro-pores and micro-pores created in silicon substrate. The micromodel pore surface was sputter deposited with a thin layer (230 nm) of hematite. The hematite in the micromodel was reduced by injecting pH-varying solutions containing a reduced form of flavin mononucleotide (FMNH2), a biogenic soluble electron transfer mediator produced by Shewanella species. The reduction kinetics was determined by measuring effluent Fe(II) concentration and by spectroscopically monitoring the hematite dissolution front in the micromodel. Batch experiment was also performed to estimate the hematite reduction rate under the well-mixed condition. The results showed a significant spatial variation in local redox reaction rate that was controlled by the coupled diffusion and reaction. The overall rate of the redox reaction in the micromodel required a three-domain numerical model to effectively describe with distinctive rate parameters in different pore domains. Results from this study demonstrated the important scaling effect when extrapolating geochemical or biogeochemical reaction rate from batch reactor to porous media and indicated a significant control of physical transport mechanisms on the reaction rate scaling.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1086412
• Report Number(s): PNNL-SA-91211; KP1702030
• Journal Information: Environmental Science & Technology, 47(9):4131-4139, Journal Name: Environmental Science & Technology, 47(9):4131-4139
• Country of Publication: United States
• Language: English

Related Subjects

Reactive transport
porous media
hematite