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mcardenas

Modeling kinetic Si dissolution in column experiments

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I am working on a final project in a course, and am having some difficulty interpreting the output from GWB. My input files are below. My question boils down to how geochemist workbench deals with the "time" component on the basis species page, and the "reactants times" on the reactants page when dealing with a flow-through model.

 

I have found the residence time of a conservative tracer in my column, which is ~164 minutes. Over the course of my column experiments, which typically last ~5 days, I react ~44 pore volumes. To incorporate this information into the model, I have used both 164 minutes (residence time) and 120 hours (average experiment time). On the reactants page, I said to react 44 times. But I don't know what GWB is reacting in that case. If someone would be able to advise me on the best way to incorporate all the known data into my system, I'd appreciate any help.

 

In the end, I want to run a series of these to see how long it takes to dissolve 15.59 cm^3 or 23 grams of silicate glass.

 

Thanks,

 

MC

SiDiss1.rea

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Hello MC,

 

The start and end times you set on the Basis pane define the time span of your kinetic reaction path simulation (total experiment time). The reactants times value is a multiplier (default 1) for the mass of any reactant on the Reactants pane, whether it’s solvent water, species, minerals, or gases. For example, if you want to change the amount of any mineral reacted into the fluid; you can do so for each individual mineral on the Reactants pane. Or, if the proportions of each mineral remain the same, you can just adjust the reactants times value.

 

It sounds like you may want to set up a flush model, where a reactant fluid that you define displaces the initial porewater (the fluid defined on the Basis pane). The total experiment time and the value for reactants times imply a certain residence time when using the flush model. For example, if the pore fluid is replaced 40 times over the course of 120 hours, the residence time would be 3 hours. You can read more on flow-through and flush models in section 3.2 and 3.3 of the GWB Reaction Modeling Guide.

 

Kind regards,

 

Katelyn

Aqueous Solutions LLC

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