Adding H2O2 for a new mineral (Studtite)

[Jungjin Kim]

Hello.

 

I'm trying to get a stability diagram for studtite (UO₄^. 4H₂O).

 

The studtite solubility reaction : UO4 ^. 4H₂O + 2H⁺ <--> UO₂²⁺ + 4H₂O + H₂O₂

 

But I can't find H2O2 in the 'Thermo.com.V8.R6+.tdat".

 

So, how can I add H2O2 to that GWB data.

 

 

Sincerely yours,

 

Jungjin Kim

[Brian Farrell]

Hello Jungjin Kim,

 

I apologize for taking so long to respond. I have been in and out of the office conducting training workshops.

 

I think you want to add H2O2 as a new redox couple: H2O2 = H2O + .5 O2(aq). You'll need to search the literature for thermodynamic data for that reaction.

 

Hope this helps,

 

Brian Farrell

Aqueous Solutions

[Jungjin Kim]

Thanks Brian Farrell,

 

 

I found the equilibrium constant for that reaction on this site: http://www.h2o2.com/technical-library/physical-chemical-properties/thermodynamic-properties/default.aspx?pid=40&name=Decomposition-Products

 

But there are no ion size of H2O2. There is only molecular radius (1.32 A) in a literature.

 

So, dose the ion size in the TEdit mean ion radius?

 

Thanks.

 

Jungjin Kim

[Brian Farrell]

Hi Jungjin Kim,

Although it's called the ion size parameter, in practice it is determined by fitting the Debye-Huckel equation to experimental data.

Polar neutral species are most commonly assigned activity coefficients of unity. As noted in the Thermo Datasets Appendix of the GWB Reference Manual, the ion size parameter has special meaning for neutrally charged aqueous species. To specify an activity coefficient of one for neutral species, you set the ion size parameter to any number greater than 0.

Regards,

Brian