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Qianwei

Could not find the La+++ in the ion list

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Hi there,

 

I am just a new user of GWB student version and I wonder how could I find the La+++ in the species list. Thank you very much!

 

Qianwei

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Hello Qianwei,

 

You can use TEdit, the graphical thermo data editor, to see which dataset may be appropriate for your work. To load a given dataset into the GWB program go to File -> Open -> Thermo Data… If there’s a species that’s not included in one dataset, you can easily copy a species from one dataset to another, or add data from the literature. For more information, see the TEdit section in the GWB Essentials Guide. You can also view tutorials on how to edit thermo datasets here.

 

Kind regards,

Katelyn

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Hello Qianwei,

 

You can use TEdit, the graphical thermo data editor, to see which dataset may be appropriate for your work. To load a given dataset into the GWB program go to File -> Open -> Thermo Data… If there’s a species that’s not included in one dataset, you can easily copy a species from one dataset to another, or add data from the literature. For more information, see the TEdit section in the GWB Essentials Guide. You can also view tutorials on how to edit thermo datasets here.

 

Kind regards,

Katelyn

Hi Katelyn,

 

Many thanks for your reply. And I tried to use another thermo dataset in with Act2 and I found the La+++ I wanted, but I got another problem when I tried to draw the pH-Eh diagram. There is no minerals's state in the diagram and it always show the La++ without La+++ which is more stable. Could you help me with this? I used the SpecE8 for the activity calculation of La+++ ion but the results always come to be the activity of La++. Thanks again.

 

Regards,

 

Qianwei

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Hello Qianwei,


Can you please attach your Act2 (.ac2) and your SpecE8 file (.sp8)? That way I can take a better look at the issue you are having.


Thank you,


Katelyn

Aqueous Solutions LLC

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Hello Qianwei,

 

You can use TEdit, the graphical thermo data editor, to see which dataset may be appropriate for your work. To load a given dataset into the GWB program go to File -> Open -> Thermo Data… If there’s a species that’s not included in one dataset, you can easily copy a species from one dataset to another, or add data from the literature. For more information, see the TEdit section in the GWB Essentials Guide. You can also view tutorials on how to edit thermo datasets here.

 

Kind regards,

Katelyn

 

Hello Qianwei,

 

Can you please attach your Act2 (.ac2) and your SpecE8 file (.sp8)? That way I can take a better look at the issue you are having.

 

Thank you,

 

Katelyn

Aqueous Solutions LLC

Hi Katelyn,

 

Thank you for your help and attached is my result.

 

Regards,

 

Qianwei

Act results.ac2

SpecE8 results.sp8

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Hello Qianwei,


Are you sure that La+++ should be more stable than La++? Try taking a look at the reaction between La+++ and La++ in the thermo dataset you’re using and verify that the equilibrium constant makes sense. If it doesn’t seem correct, check the literature and modify the thermo dataset if necessary. The “alter” function is a useful feature of the GWB programs. It allows you to temporarily alter the log K for a reaction without permanently modifying your thermo dataset. You can access the alter settings from the Config – Alter log K dialog.


You can also suppress species that are unlikely to form using the “suppress” command. Finally, if you’d like to consider only one oxidation state of La, try disabling the redox couple between La+++ and La++. You can read more about redox couples in the Essentials Guide, Section 7.3 Redox disequilibrium.


Kind regards,


Katelyn

Aqueous Solutions LLC

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Hello Qianwei,
Are you sure that La+++ should be more stable than La++? Try taking a look at the reaction between La+++ and La++ in the thermo dataset you’re using and verify that the equilibrium constant makes sense. If it doesn’t seem correct, check the literature and modify the thermo dataset if necessary. The “alter” function is a useful feature of the GWB programs. It allows you to temporarily alter the log K for a reaction without permanently modifying your thermo dataset. You can access the alter settings from the Config – Alter log K dialog.
You can also suppress species that are unlikely to form using the “suppress” command. Finally, if you’d like to consider only one oxidation state of La, try disabling the redox couple between La+++ and La++. You can read more about redox couples in the Essentials Guide, Section 7.3 Redox disequilibrium.
Kind regards,
Katelyn
Aqueous Solutions LLC

 

Hi Katelyn,

 

Thank you for your help and now I got another problem. I applied the log activity of species in SpecE8 in the Act2 program, but the results does not match at all. According to the results of SpecE8, the only saturation mineral is La2(CO3)3-8H2O while in the pH-Eh diagram, there is no mineral precipitation. Could you help me figure out what the problem is? Attached is my results. Thank you very much!

 

Regards,

 

Qianwei

Act2.ac2

specE8.sp8

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Hello Qianwei,

 

In your Act2 model both oxidation states La(II) and La(III) are allowed to form since your basis includes Eh (as the y-axis variable), a measure of oxidation state. However, in your SpecE8 model you only include La+++ and no measure of oxidation state, so there is no way La++ can be considered in your system. Make sure your description of redox chemistry is consistent between both of your applications, Act2 and SpecE8. For more information, take a look at Section 7.3 Redox disequilibrium in the GWB Essentials Guide or Chapter 7 in the Geochemical and Biogeochemical Reaction Modeling text.

 

Kind regards,

 

Katelyn

Aqueous Solutions LLC

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