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About how to add new mineral to database and run x1t


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Our client wants to add a new mineral named "Biotite" to GWB thermo database.

Please download the zip file ( https://drive.google.com/file/d/1p-UECLJphZf6eaaFUtb77plCg_7i3WMe/view?usp=sharing ) which has the following information:

1. thermo.com.V8.R6+_Dr. Lee.tdat   <- They create the new mineral by themselves but cannot ensure if it is OK. 

2.Implications of Grain-Scale Mineralogical Heterogeneity for Radionuclide Transport in Fractured Media.pdf <- They want to create and simulate the same as Table 2.

3. Case study_Cs transport_20181015.x1t  <- They create the X1t file.

4. kyllnen2014_Modeling of cesium sorption on biotite using cation exchange selectivity coefficients.pdf <- The mineral "Biotite" reference.

Please help us.

Thanks a lot.



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Guest Melika Sharifi

Dear John,

From the dataset you sent us, it looks like Biotite has not been properly added to the dataset. To add a mineral or an aqueous species, you'll need to supply the necessary reaction between the new species/mineral and the basis species in the dataset, as well as the log Ks (from literature) for that reaction at different temperatures.

Sections 9.2.3 and 9.2.4 in the GWB Essentials guide describe how to add reactions to your dataset using TEdit. I think you'll also find the tutorial entitled "How do I add new elements, species, and reactions" helpful.



Melika Sharifi

Aqueous Solutions LLC

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Hi John,
I just have a little bit to add to the discussion, for when you get around to the ion exchange reactions. Ion exchange models aren’t tied to specific minerals the way a two-layer surface complexation dataset is. Instead, you set the exchange capacity of the surface in X1t directly (in units like meq) or you set it per gram of minerals (in units like meq/g rock). In the latter case, the total mineral mass is the sum of equilibrium, kinetic, and inert minerals in the system. If you’re only interested in the surface properties of biotite, it might not be necessary to explicitly include Biotite in your calculation, so long as you specify the correct surface reactions and exchange capacity.
You can only specify one basis surface species per ion exchange dataset, so you’ll need to create three separate surface datasets, one for each site (e.g. planar, intermediate, and frayed-edge). Then, you’d load each surface dataset into X1t and specify the exchange capacity for each, based on their percentage of the total exchange capacity. Each surface dataset will need a unique type (e.g. Biotite planar, Biotite intermediate, and Biotite frayed-edge) and unique species names (e.g. >X:Na, >XInt:Na, and >XFES:Na). Finally, you should be sure to set the selectivity coefficient as a linear value, not a log value. The value is converted to log format internally. For more information, please see 2.5.4 Ion Exchange and 7.6.2 Ion Exchange in the GWB Essentials Guide, as well as the example dataset IonEx.sdat included in the Gtdata folder.
Hope this helps,
Brian Farrell
Aqueous Solutions LLC
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