Initializing a system in which some ions are immobilized.

[Aditya-Puru]

Hii there,
I want to build a system in which some ions are immobilized so when I use X1t for reactive transport it wont wash away and even if it get reacted with some other ions from the aqueous solution being passed, the final product remains attached to the system so I can measure the quantity of it at the end of some period of time.

Please let me know how should I go about it.
Thanks.

[Jia Wang]

Hello,

It is difficult to say without understanding the type of problem you are trying to study. Is there a specific process you are attempting to represent with the immobilized ion? To help you get started, here are some configurations and features designed to model specific mechanisms that may interest you.

For instance, the software allows a fraction of the domain to function as stagnant zones, enabling solutes to diffuse into and out of these zones. This model is known as the dual porosity model. Refer to the GWB Reactive Transport Modeling guide for more information in sections 2.17 and 3.12.

Additionally, the software can account for various types of surface complexation reactions, where ions can form surface complexes on mineral surfaces. A comprehensive description of all surface complexation models can be found in section 2.6 of the GWB Essentials guide.

There are special configurations that are available in React, an application for modeling dynamic systems in a single node system. A flow-through type model allows the user to separate precipitated minerals or solid solution end members from back dissolving. These special configurations are not available in the reactive transport applications. Please see section 2 for more information on React.

If you require further assistance with troubleshooting, please provide a more detailed description of what you're trying to achieve, along with any available input and thermodynamic files.

Hope this helps,
Jia Wang
Aqueous Solutions LLC

[Aditya-Puru]

Thanks for the reply Jia, 
I want to model an acidic organic polymer immobilized in the soil and use its acid/base properties in reactive transport. What would be a suitable approach to achieving this?


Basically from my understanding reactants get washed away from the system with continuous flow of fluid in X1t. I don't want that to happen to these polymers and hence acid groups.

How about creating a polymer in the "thermo database" with multiple carboxylic acid groups attached to it and then defining acid/base reactions of that polymer in database?
 

[Jia Wang]

Hello Aditya,

Thank you for the additional information. The GWB programs do not allow a reactant to be immobilized without some mechanism. For example, an aqueous species can adsorb or precipitate which will allow it to be removed from the fluid in a flowing system.

What you described sounds a lot like how surface species are simulated in surface complexation reactions in the GWB. I would recommend looking into setting up either langmuir or non-electrostatic two-layer surface complexation type datasets. Both types will allow you to set up basis surface species, which are considered to be immobile surface sites unless otherwise specified. You can set up a surface complexation dataset with the basis species set as your polymers and add reactions to your surface dataset that reacts to form on that surface site. Complexes that form on these surfaces will not be transported.

The best place to get started is to learn about the langmuir model and the two-layer model is in section 2.6 of the GWB Essentials Guide. You can see examples of both types in the Gtdata folder that comes installed with the software.

Hope this helps,
Jia