How to model reaction of H2S and SO3- - ?

[Oleh Weres]

I am using a data base which contains H2S and sulfite as redox species, both tied to sulfate as a basis species.

How do I model in REACT the reaction of H2S with sulfite ?  I need to decouple them from sulfate in order to be able to enter them, but then they won't react !

[Oleh Weres]

I also have thiosulfate, trithionate, etc., in my data base, but they don't show up, even though they remain couple to and through sulfate.

[Brian Farrell]

Hi Oleh, 

One strategy would be to set a simple kinetic rate law for the redox reaction between H2S and sulfite. If kinetic parameters are unknown, or time isn't particularly important, you could just use arbitrary values and ignore the time.

If you want to use an equilibrium model, though, you'll probably have to rebalance the coupling reactions in your thermo dataset. Instead of coupling redox species H2S and sulfite to the basis species sulfate, you could set up a dataset with H2S or sulfite as a basis species, and the other two coupled to it. The TEdit app provides a convenient way to do this. It will rebalance any reactions that would be affected. For details, please see section 9.2.8, Exchanging species, in the GWB Essentials Guide.

I'd have to see your script and thermo dataset to see why the other species aren't being loaded in your simulation.

Finally, it's easy to miss posts in the archive. In the future, please add new topics to the main section of the GWB forum.

Hope this helps,

Brian Farrell
Aqueous Solutions LLC