Modeling high pH systems

[Nancy]

Hello,

I’m a sporadic user of GWB so basically a beginner, once again, with fading knowledge on geochemistry from grad school. Your forum discussions are a great learning tool so thank you for them. I am trying to model silica at STP but high pH (pH=12-14, ie: concrete pore solution) with excess cations of K, Ca, Na, Li, etc. How valid is the default thermodynamic database at high pH in GWB 8.0. Would one of the other datasets provided be more valid? Do I need to develop some of my own values? If so which thermo-values and modeled behavior can I trust and which may be suspect? I am especially interested in modeling dissolution/ppt, mineral surface complexing and ion exchange.

 

Thank you for any guidance you can provide.

Nancy

[Tom Meuzelaar]

Hi Nancy:

 

Welcome to the forum.

 

I don't have much knowledge about the thermo data at that pH range. Hopefully, someone with a better background can address this.

 

I can, however, point out two references to get you started:

 

1. The reference for the LLNL database: "Delany, J.M. and Lundeen, S.R. (1990) The LLNL thermochemical database, Lawrence Livermore National Laboratory Report URCL-21658, 150 p"
   
2. In the extended LLNL database (thermo.com.v8.r6+.dat), a reference to the data source is given on a species by species basis.
   

 

Hope that helps,

 

Tom Meuzelaar

RockWare, Inc.