Conceptual Models > Database selection and modification

Adding ethanol, CaCl2 and Na2CO3 to database

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maria15143:
Hi,

I'm quite new to PHREEQC, but I'm trying to define two solutions in which in each of them I'm adding ethanol and Na2CO3. I'm using the database phreeqc. Like I saw that the chemicals I'm trying to add are not defined in the database, I tried to add them by doing this:

SOLUTION 1
    temp      23
    pH        7.2 charge
    pe     4
    redox     pe
    units     ppm
    density   1 calculate
    Ca        136
    Cl        3.5
    K         2.3
    Mg        32
    N(5)      87   as   NO3
    Na        50.6
    S(6)      115.2   as   SO4
    -water    1 # kg
    END
USE solution 1
REACTION 1
    C2H6O      1 #DOC
    1.3 millimoles
    Na2CO3     1 #DIC
    0.82 millimoles
END       

However, when I try to mix this with another solution, it considers only the Solution 1 and not the chemicals added in reaction 1.  I know the best thing to do is to just modify the database, but I just don't know how and I would have to invert a great deal of time doing it. Is there a way to save the "output" solution of the reaction as a new solution and mix it? Does anyone have a solution for this? Thanks!

dlparkhurst:
By adding ethanol as C2H6O, it will enter solution as some combination of C(4) (carbonate) and C(-4) (methane), but will not be ethanol. This approach is appropriate if you want to model degradation of ethanol.

If you want Ethanol to be stable in solution, then you should use the approach in the attached script. However, it will more or less just sit in solution unless you explicitly react it with REACTION or KINETICS. If you want ethanol to react, the most likely reaction would be simulated as follows:


--- Code: ---REACTION
Ethanol -1
C2H6O 1
0.0005 moles

--- End code ---

As for Na2CO3, it should, in fact, dissolve and react to equilibrium, so it can be added directly, as shown in the script.


--- Code: ---SOLUTION_MASTER_SPECIES
Ethanol Ethanol 0 Ethanol 46.1
SOLUTION_SPECIES
Ethanol = Ethanol
log_k 0
END

SOLUTION 1
    temp      23
    pH        7.2 charge
    pe     4
    redox     pe
    units     ppm
    density   1 calculate
    Ca        136
    Cl        3.5
    K         2.3
    Mg        32
    N(5)      87   as   NO3
    Na        50.6
    S(6)      115.2   as   SO4
    -water    1 # kg
    END
USE solution 1
REACTION 1
    Ethanol      1.3 #DOC
    Na2CO3       0.82 #DIC
    1 millimole
END

--- End code ---

If you want to save the result of this calculation for mixing with another solution, you need to use the SAVE keyword.


--- Code: ---...
SAVE solution 3
END

--- End code ---

If you have a solution 2 that you are reacting and saving as solution 4, then you could mix the two:


--- Code: ---END
MIX
3 0.5
4 0.5
END

--- End code ---

maria15143:
Great, I understand. Thank you very much, I will try it.

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