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Heavy Metal Hazards
Hydraulic fracturing, or fracking, is the dominant process by which we obtain natural gas in the US. This process involves injecting large volumes of fracking fluid into a shale (rock) formation. Much of this fluid returns to the surface, contaminated with many trace elements from the rock. The goal of this project is to decrease the hazards of heavy metals in the returned fluids by adding compounds that would immobilize these metals. Experiments exposed samples from the Marcellus Shale to hydraulic fracking fluid with several isomers of bipyridine. Analysis of the fluid from these experiments showed that by bipyridine decreases uranium concentration in solution significantly. The SEM images show formation of novel mineral phases in the presence of bipyridine. These phases are absent in fracking fluid without bipyridine and in a water control.
This image shows shale that has been incubated with hydraulic fracturing fluid (HFF) and 2,2’ bipyridine. The needle-like crystals seen are not present in shale incubated in HFF without bipyridine. The addition of bipyridine also decreases the concentration of uranium in the aqueous phase, suggesting that these crystals are associated with formation of new uranium-containing minerals and/or sorption of uranium to these newly formed minerals. The EDX map on the right shows that the newly formed minerals contain Ca and S, suggesting gypsum, which can form crystals of this morphology.
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