RE1: Transport/Precipitation Coupling in Porous Media
Lead: George Redden (INL)
Participants: Don Fox (INL), James Henriksen (INL), Tsigabu Gebrehiwet (U of Idaho), Tim Johnson (PNNL), Yoshiko Fujita (INL), Karen Wright (INL)
Research Element 1 is the core component of the program in which a sequence of physical experimental campaigns are designed and conducted to examine the relationships between reactant mixing, the evolution of spatial distributions of mineral precipitates and soluble reaction products, and changes in the mobility of trace metal contaminants in porous media systems at multiple scales.
Experiment set 1: In situ Reactant Generation
Hypothesis: In situ production of a mineral-forming constituent will result in delaying the onset of precipitation from the time of amendment injection, and prcipitate distributions will be functions of the relative rates of reactant generation, precipitation and solute transport.
For our SFA, we chose to use calcium carbonate as the model mineral system and the enzyme catalyzed urea hydrolysis as the carbonate-genrating mechanism. 1-D column experiments have been conducted as a prelude to 2-D flow cell experiments. Under different flow conditions and chemical composition of the the solutions, th goals are to investigate the temporal and spatial distribution of precipitation which is determined by the complex coupled interactions between physical and chemical processes, and to study the modified mobility of trace metal by a combination of mechanisms: co-precipitation, encapsulation, and isolation from flow and /or competitive desorption.
The physical set up of the experiments are depicted in the flowing schematic figure.
Figure The schematic of column experiment used in the "in situ reactant production" campaign.