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X2t leaching modeling

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I'm having troubles with getting my model run in X2t. I will very appreciate your help.

I would like to simulate a leachate from a tailing pile after a storm event (acid mine drainage).

But when I run my model it gives me a mistake (N-R didn't converge after 999 its....).

The contaminants are Zn, Cd, and Pb (there is another thing. I didn't see Cd in the dropdown menu where species are selected).

I assumed that the concentrations are uniform along the pile since there is average concentration data. For my inlet, I used species of sinthetic rainwater.

Is it possible to model what will leach after a storm event to the toe of the tailing pile?


Thank you very much in advance.


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Hello Anzhelika,


I moved your topic from the archive of old posts to the forum for new queries.


Keep in mind that the thermodynamic dataset you choose for your simulations is part of the input to your model. Some thermodynamic data may be incomplete or inaccurate. The databases we do have are a result of experimental work by countless labs and individuals, and the work it took to compile all this data from different sources into a single (hopefully internally consistent) database. I assume you are using the default thermodynamic dataset, thermo.dat, which does not contain Cd. You'll either want to add Cd species and minerals to the dataset (see the GWB Reference Manual - Thermo Data Appendix, or many of the posts on the main forum page or in the database section of the archives) or switch to a dataset that contains Cd species (like thermo.com.V8.R6+.dat).


When the program can't converge on a solution, it can be for a number of reasons. Your system may be far from equilibrium, for example, and trying to solve for the equilibrium state might be difficult or impossible. If you post an example script, someone might be able to take a look and make some suggestions.


Hope this helps,

Brian Farrell

Aqueous Solutions LLC

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Thank you very much for your help.

I changed to thermo.com.V8.R6+.dat thermodynamic database.

But I still can't get my model running.

I'm sending my file and will very very appreciate if you or somebody else take a look at it.

In the initial pane, I put concentrations of the contaminants (they are given from sampling analysis) and 10 % volume of Fe2(SO4)3 (I was going to use Fe(OH)3 but the program didn't like it). In the inlet pane, I put concentrations of ions in a synthetic rain water.

I'd like to simulate what concentrations of the matals will be at the toe of the tailing pile in order to model a bioreactor for treatment.


Thank you very much.

Anzhelika. Holy Moses.x2t

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Hi Anzhelika,


One thing I notice right away is that you have zero values entered for some analytes in the Initial and Inlet panes. Because of the way the program solves for the distribution of chemical mass, 0 values cannot be used. You should set a negligibly small concentration for any analyte that has a measured 0 value in either your initial or inlet fluid.


What do you hope to use the Fe(OH)3/ Fe2(SO4)3 for?


Hope this helps,


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Hi Brian,


Thank you very much. I will try to do it that way right now.

I was going to use Fe(OH)3/Fe2(SO4)3 for adsorption because iron hydroxides may adsorb some of the contaminants. But I think not to include it now because they can be washed off with the rain flow.

I don't have much data for this project. I was just assuming that the surface of the tailing pile is comprised mostly of sulfates because of oxidation.


I will lwt you know how it goes.

Thanks a lot, Brian!

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Hi Brian,


I got my model running. Thank you very much for your help.

You're right. It didn't like zeros for concentrations. And I also had to put extra Na ion with a small concentration because the program gave me that mistake with a large SO4-- residual.

I posted an updated model if you are interested.


Thank you very much! I appreciate your help.



Holy Moses.x2t

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