Pourbeix diagram using Pitzer

[Nikoleta]

Hello,

 

I am using the Standard Edition and I compiled my database including Pitzer coefficients as I am using high saline conditions, up to saturation for NaCl and MgCl2. I wanted to draw a stability diagram for Iron in Act2 but it only allows the Debye Model and doesnt load the database using the HMV model. I saw this also in manual that act 2 doesnt support pitzer, meaning I cant use act2 to draw the stability diagram for iron in MgCl2. my question is: are there any other tools which I could use, using the HMV model to obtain the stability diagram.

 

Many Thanks,

 

Nikoleta

[Brian Farrell]

Hi Nikoleta,

 

You can use Pitzer datasets with Act2. The app will work properly with the data it's given, but the results may not be especially interesting and can be a little misleading. Unlike Debye-Hückel based models, which account for the distribution of aqueous species explicitly, Pitzer models by design include almost no speciation. Most species are treated as if they’re completely ionized; in most published datasets only a limited number of basis species protonate and deprotonate or form ion pairs that are worth including as distinct species. You’re much better off using a Debye-Hückel dataset instead of a Pitzer dataset for drawing diagrams.

When you load a Pitzer dataset, the message that pops up simply alerts you that you’re not using a true speciation (Debye-Hückel) model. Your chosen dataset is in fact loaded into the app and used to construct the diagram. You can verify this by going to File – File Properties – Thermo Data.

By the way, the current release includes several improvements to the Pitzer equations implemented in GWB8. The Pitzer models now accept species of any charge. Additionally, the form of the temperature polynomial for virial coefficients in the H-M-W model has been extended.

Regards,

Brian Farrell

Aqueous Solutions LLC