Custom mineral phase

[Jay Chou]

Hello researchers：
I want to use the Pitzer database for simulation, but there is no desired mineral phase in it。
I want to know what data is needed to define mineral facies for mineral facies that do not exist in the database.
For example,Li2SO4H2O、Li₂CO₃
Take  Li₂CO₃  as an example
I have the following definitions（The data are examples）：

SOLUTION_MASTER_SPECIES
Li  Li+   0    6.94

SOLUTION_SPECIES
Li+ =Li+
log_k   0

PHASES
lithium carbonate
2Li+ +CO32-=Li2CO32-
log_k      -3.490
delta_h   -18.630 kcal
I just came into contact with this software
I don't know if the above operation is correct
Thank you for your reply！

[dlparkhurst]

There is a manual, the pitzer.dat database, and many examples you can look at.

PHREEQC has some conventions you must use. A charge of -2 on CO3 must be written as CO3-2 or CO3--, not CO32-. PHASES definitions use dissociation reactions. Reactions are checked for element and charge balance. Phase names cannot contain spaces. The script below will run with pitzer.dat.

Li is defined within the pitzer.dat database with SOLUTION_MASTER_SPECIES and Li+ is defined with SOLUTION_SPECIES; so, you do not need to redefine them unless you want to change something. However, there  are only a limited number of interaction coefficients defined in the PITZER data block of pitzer.dat for Li+ and none for Li--CO3-2 interactions. I think you would need to define some to model Li2CO3 solubility accurately with that database. Perhaps you can find some parameters in the literature. You should compare calculated solubility of Li2CO3 with experimental values.

Code: [Select]

PHASES
Li2CO3
Li2CO3 = 2Li+ + CO3-2
log_k      -3.490
delta_h   -18.630 kcal
END
SOLUTION 1
END
EQUILIBRIUM_PHASES 1
Li2CO3 0 10
END
USE solution 1
USE equilibrium_phases 1
END


[Jay Chou]

Thank you very much for your reply
I have another question:
1. If I only want to find the Li2CO3 saturation index, can I only define it in the phases module
log_ k    delta_ H these two parameters,
2. If not, what parameters do I need to know.
Thank you very much for your reply these days

[dlparkhurst]

You only need to define a balanced reaction and a log_k for Li2CO3 in PHASES input, and a saturation index will be calculated if both Li and C are present in the solution.

If you want to use a temperature other than 25 C, you should also define a delta H or an analytical expression; otherwise the log K will be constant at all temperatures.