Exclusion effects in model

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Helya
Posts: 3
Joined: Mon May 10, 2021 2:02 pm
Location: Canada

Re: Exclusion effects in model

Post by Helya » Tue May 11, 2021 8:58 am

I appreciate your prompt response. It was really helpful!
I used the two kinetic sorption site model with the theta_imob specified (I got the estimated theta_imob from my tracer data simulation, it is 0.04[-]), as you explained the model, it is calculating as it should, it's just not perfectly matched with my experimental data. The simulated and experimental BTCs are attached here. The earlier arrival of the simulated BTC reflects NP exclusion in the model and the tailing looks Ok.
I think I can live with this result though!


However, just out of curiosity, what would possibly get the simulated tail to fit more with the experimental data? I believe if the model could consider a mass transfer rate between the mobile and immobile regions (if kinetic reactions were allowed in immobile regions as well), I could get a better fit, right?
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Jirka
Posts: 5216
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Exclusion effects in model

Post by Jirka » Tue May 11, 2021 5:02 pm

Looking at your BTC, it does not seem to me that you need the physical-nonequilibrium model (i.e., immobile water). The model predicts earlier solute arrival than the data. I would drop it and work with a “two kinetic site” model. J. 

Helya
Posts: 3
Joined: Mon May 10, 2021 2:02 pm
Location: Canada

Re: Exclusion effects in model

Post by Helya » Tue May 11, 2021 7:45 pm

Right! Based on the comparison between the modeled (using attachment/detachment+specified por_imob) and the experimental data, seems like no exclusion happened during the transport in unsaturated porous media! Hence, physical non-equilibrium should be dropped!
However based on my experimental tracer data, a long tail was observed in tracer BTC! and it was the reason I wanted to use the MIM model.
To conclude, even if any physical non-equilibrium transport "actually" happened in the column, I would ignore it (i.e., ignore the tracer BTC tail) and just use the attachment/detachment model which better describes my colloid transport behavior. I believe I have no other better option.
If anyone has a suggestion in such a complicated case, I would appreciate it if he/she shares it here.

Thanks,

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