Using the results of the first simulation for the second one

[Tamirian]

Hi every one,

I have this case of a surface aged in solution 1, then solution 2 has been introduced to the system and I need to calculate the new zeta potential . I have created a surface in equilibration with solution 1, then I used the "save" command to save the surface after equilibration with solution 1 as surface 2. Then, I used surface 2 in my second simulation. I am very new to PHREEQC and I do not know if I am on the right path. Is it the right way to calculate the new zeta potential after exposure to the new solution? I wonder if you could help me. You can see my coding below:

SURFACE_MASTER_SPECIES
    Inf_co        Inf_coOH     
    Inf_n         Inf_nH+     

SURFACE_SPECIES
Inf_nH+ = Inf_n + H+
    log_k     -6
    delta_h   34 kJ
Inf_nH+ = Inf_nH+
    log_k     0
Inf_coOH = Inf_coO- + H+
    log_k     -5
Inf_coOH = Inf_coOH
    log_k     0
Ca+2 + Inf_coOH = Inf_coOCa+ + H+
    log_k     -3.8
    delta_h   1.171 kJ
SURFACE 1
    -sites DENSITY
    Inf_coOH    1         10        100
    Inf_nH+    1
SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mol/l
    density   1
    Ca        0.1
    Cl        1
    Na        1
    -water    1 # kg

SAVE surface 2
END

USE surface 2

SOLUTION 2
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mol/l
    density   1
    Ca        0.2
    Cl        0.2
    Na        0.2
    -water    1 # kg


 

[dlparkhurst]

You are correct until you defined a new SOLUTION 2. The new solution 2 will first be speciated, and then it will be the current solution 2 that will be USEd in the reaction calculation, rather than the one that was SAVEd from the last reaction calculation.

Also, the charge (Inf_nH+    1) is ignored in a SURFACE definition. It is recommended to use charge balanced formulas, like Inf_coOH, or define the surface in equilibrium with a solution (-equilibrium).

[Tamirian]

Thank yo very much for your reply. Just one point that, my only concern is the surface, not the solution. I want to use surface 1 but after reaction with solution 1.  I saved it as surface 2. I would like to know if the save command would let me use "the surface 1 after reaction with solution 1" as surface 2 in the second simulation. My filed is petroleum engineering and I am trying to model a surface in equilibrium with formation water (solution 1) which would be exposed to new solution (solution 2) after water injection. I hope I am making sense!!

[dlparkhurst]

Yes, you can use SAVE and USE for solutions and (or) reactants, such as SURFACE. If you want to be clear, just define one entity at a time before an END, and then explicitly define the reactions with USE

SOLUTION 1
...
END
SURFACE 1
...
END
USE solution 1
USE surface 1
SAVE solution 2
SAVE surface 2
END
REACTION 2
END
USE solution 2
USE surface 2
USE reaction 2
END