Formation of Iron-Molybdenum-Sulfide Phase(s) in Anoxic Natural Waters

Presenter Information

Emma Stong, Minnesota State University - Mankato

Location

CSU Ballroom

Start Date

21-4-2014 10:00 AM

End Date

21-4-2014 11:30 AM

Student's Major

Chemistry and Geology

Student's College

Science, Engineering and Technology

Mentor's Name

Trent Vorlicek

Mentor's Email Address

trent.vorlicek@mnsu.edu

Mentor's Department

Chemistry and Geology

Mentor's College

Science, Engineering and Technology

Description

Coastal anoxia is a proliferating environmental problem. Knowledge of the controls on anoxic incidents may assist in creating strategies for mitigating dead zone development. While the unique geochemistry of Mo may provide the means to acquiring this knowledge, interpreting Mo records is hampered by an incomplete understanding of Mo deposition chemistry. While thiomolybdates (MoO4-nSn2- ; n = 0-4) are believed to play a role in Mo removal, the final sedimentary product remains unknown. Some suggest Mo deposition ultimately involves uptake of MoO4-nSn2- by pyrite surfaces. Others claim sequestration involves precipitation of an iron-molybdenum-sulfide (Fe-Mo-S) mineral. This research aims to begin resolving such disputes. Buffered solutions initially containing 70 mM Fe2+, 70 mM MoS42-, and SS2- = 20 mM at pH = 8.5 experience quantitative loss of SFe and SMo, indicating precipitation of an Fe-Mo-S phase(s). Ongoing experiments are designed to characterize the Fe-Mo-S solid(s) and quantify stability constant(s).