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Luis C. Savanguane

Kinetic of complexation and sorption model

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Dear all!
 
I am Luis Savanguane, learning how to use GWB.
 
1. I want to know how GWB calculate pH, species concentration and mineral precipitation after get the kinetic reaction rate on kinetic of complexation and sorption model (react)? 
    Can I get the equations to quantify species contraction and pH change? 
2. How to introduce (consider)  inhibitors on modeling.
3. How to add mineral as reactant ?
 
Sincerely 
 

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Hello Luis,

I would suggest you start by looking at the equations for kinetic complexation in Section 4.4 of the Reaction Modeling Guide. React can trace the association and dissociation of any number of aqueous complexes, as well as surface complexes. An additional resource would be the Geochemical and Biogeochemical Reaction Modeling text that may provide details on governing equations and examples in The GWB. In particular, you may be interested in Chapter 10 Surface Complexation.

You can certainly consider inhibiting and promoting species in your simulation. The addition of an inhibiting or promoting species modifies the rate law for the reaction. To enable promoting or inhibiting species, you can add species in the reactants pane for the kinetic reaction of your choice and choose the power to which this species is raised to. Specifically for inhibiting species, the power raised have a negative value. For more information, please refer to section 4.2 in the Reaction Modeling guide for more information.

You can add mineral as a reactant in the Reactants pane for React, Phase2, X1t, and X2t. A mineral can be specified as a kinetic or simple mineral, where the former requires user provided rate constant and surface area constraints. A simple mineral gradually adds or removes mineral to the system and the equilibrium state is calculated at every step of the reaction. Please refer to section 3 and 4 of the Reaction Modeling guide for more information and examples.

Hope this helps.

Best regards,

Jia Wang

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Dear Jian Wang !

Thank you very much for your orientation.

  •  For how to consider the inhibitor and catalysts on modeling, your orientation is very helpful. thank you. 

But for the other issue, maybe I didn't clarify well

1. I intent to simulate a kinetic dissolution and precipitation of wood ash in water using react. The XRD of wood ash indicated the presence of Calcite, Brianite and Sylvite. Reactants pane doesn't have Brianite. So how to include this mineral (brianite) on simulation? How to add this mineral on reactants pane? 

Sorry for disturbing you. 

Sincerely 

Luis  

 

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Hello Luis,

Thank you for the clarification. The thermo databases distributed along with the GWB software contain a vast amount of thermodynamic information for minerals and aqueous species. However, when a mineral is not in the database (in your case brianite), you will have to add the mineral and its thermodynamic parameters manually. You can conveniently do so by using the TEdit application. Once you have successfully added the mineral to the database, it will be available for selecting as a reactant. Please refer to section 9.1 Getting started with Tedit and 9.2 Working with datasets of the GWB Essentials guide for more information and examples. 

Please post on the front page of the forum in the future. Thanks. 

Best regards,

Jia Wang

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Dear Jia Wang!

 

Thank you very much for your orientation. it very helpful. 

But now I have another problem!

What is the rate constant of Brianite and Sylvite?

Can I have some references about rates constant of Brianite and Sylvite? 

Sincerely 

 

 

 

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Hi Luis,

I believe the thermo.com.V8.R6+.tdat dataset distributed with the GWB includes thermodynamic information for sylvite. You can copy and paste the sylvite entry from the V.8.R6+ database to the database you are using. For more information on this, please refer to section 9.2.6 Transferring dataset entries in the GWB Essentials users guide.
 
I am not familiar with brianite but maybe there are some experiment data published in literature somewhere? 
 
Hope this helps.
 
Jia Wang

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Hi Luis,

I misread your post above regarding 'rate constants' as 'thermodynamic constants'. Rate constants are usually derived from laboratory experiments and published in literature. My apologies for any confusion. 

Best regards,

Jia

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8 hours ago, Jia Wang said:

Hi Luis,

I misread your post above regarding 'rate constants' as 'thermodynamic constants'. Rate constants are usually derived from laboratory experiments and published in literature. My apologies for any confusion. 

Best regards,

Jia

Dear Jia wang! 

Thank you very much.

That´s why I asked some references for who knows and can recommend . 

 I appreciate your attention

Regards   

 

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Dear Jia Wang

Happy new year 

Once again with my problems.

I am using kinetic of complexation and sorption model  rk=𝑛𝑤𝑘+∏(𝑎𝑗/𝑚𝑗 )𝑝𝑗(1−𝑄/𝐾) to predict dissolution and precipitation of wood ash. The model calculates the kinetics reaction (rk) and the results are plotted as pH changes, species, minerals concentration. I would like to know how pH, species concentration are calculated using the kinetic reaction constant (rk). Can I have equations like:

1.  pH =  rk

2.  Ca++ = rk

 

Sincerely

 

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Hi Luis, 

Happy new year to you too! Unfortunately, there’s not a set equation to calculate the concentration of these species. If you would like more information on the calculations and the methods used, please refer to the Geochemical and Biogeochemical Reaction Modeling text. 

Best regards,

Jia Wang
 

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