Sponsor – DOE
FIU’s Applied Research Center (ARC) is supporting the U.S. Department of Energy’s Hanford Site in developing a strategy to improve the efficiency of subsurface uranium stabilization through pH manipulation via NH3 gas injection.
This work is focused on long-lived uranium contamination, which is one of the key contaminants of concern for the Hanford site. Injection of reactive gases such as NH3 is an innovative remediation technology shown to decrease uranium mobility in soil and sediments.
Experiments for this task seek to identify and quantify factors controlling these processes, including: biological transformations, ammonia partitioning, and geochemical reactions. This task examines the mechanisms of potential importance using controlled laboratory systems to complement efforts underway at Pacific Northwest National Laboratory (PNNL).
When NH3 gas is injected into the subsurface, it quickly partitions between aqueous (soil moisture), solid (minerals) and gas phases. In the aqueous phase, NH4OH forms and dissociates causing a subsequent increase in pH. This manipulation can significantly alter the pore water chemistry and affect the dissolution of aluminosilicate minerals from sediments.
Furthermore, ammonia losses increase with increased temperature and pH and can be very high in dry neutral or alkaline sediments. Also, sediments rich in carbonate, which is typical for the Hanford Site, require more ammonia gas due to the existing soil buffering capacity and the formation of ammonia carbonate.
Co-precipitation of U(VI) [as uranyl (UO22+)] and Si is expected under these high pH conditions. However, the processes leading to co-precipitation and the precipitates forming under these non-equilibrium conditions are still not well understood. Moreover, the stability of possible precipitates requires additional research.
The major objective of this project is to evaluate the processes occurring during and after ammonia injection into the vadose zone, including ammonia partitioning and effects, uranium fate and mineral dissolution and precipitation.
1. Evaluate the effect of ammonia gas injection on the aqueous phase (i.e. porewater).
2. Evaluate the effect of ammonia gas injection on solid phases (i.e. mineral components).
3. Evaluate the fate of uranium during ammonia gas injection.
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Sponsor - DOE FIU’s Applied Research Center (ARC) is supporting the U.S. Department of Energy’s Hanford Site in developing a...
Sponsor - DOE FIU’s Applied Research Center (ARC) is supporting the U.S. Department of Energy’s Savannah River Site in...
Sponsor - DOE FIU’s Applied Research Center (ARC) is supporting the U.S. Department of Energy’s Hanford Site in developing...