Plotting Delta Phase Assemblage for Dissolution

[DvS95]

Hi All,

I am looking to model the full dissolution of various minerals into a solution. I have defined the solution as well as the equilibrium phases of the minerals to be dissolved to SI 0.0. I would like to increment and plot the mass of Solution 1 until the FINAL assemblage value is 0, or the DELTA assemblage value is =-INTIAL.

I know that the REACTION data block allows for incremental addition of moles of a particular element which can also be conveniently plotted, but I could not find a way to increment the mass a solution, nor how to plot the particular assemblage values for each mineral at each increment.

I have printed the input below (very novice user here, apologies for any basic blunders particularly in the USER_GRAPH function, I tried repurposing a code I found elsewhere on the forum):

Code: [Select]

DATABASE C:\Program Files (x86)\USGS\Phreeqc Interactive 3.7.1-15876\database\llnl.dat
SOLUTION 1
    temp      65
    pH        5.5
    pe        4
    redox     pe
    units     mg/l
    density   1.051
    Al        0.04
    As        13
    B         44
    Ba        32
    Br        187
    Ca        7995
    Cl(-1)    64112
    Cs        18
    F         3
    Fe        25
    K         4205
    Li        10
    Mg        109
    Mn        28
    Na   28729
    Pb        1
    Rb        27
    S(6)      157
    Si        80
    Sr   428
    Zn        7
    water    1 # kg
MIX 1
1 1000000
EQUILIBRIUM_PHASES 1
Mn(OH)2(am) 0.0 22.48
Fe(OH)2 0.0   44.51
Brucite 0.0 4801.122
Calcite 0.0 4316.249
Chalcedony 0.0 2446.738
USER_GRAPH 1
    -headings               rxn Pyrochroite Fe(OH)2 Brucite Calcite Chalcedony
    -axis_titles            "Mass of DLS Brine, kg" "FINAL Assemblage"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 GRAPH_X MIX
20 GRAPH_Y EQUI("Mn(OH)2(am)"), EQUI("Fe(OH)2"), EQUI("Brucite"), EQUI("Calcite"), EQUI("Chalcedony")
  -end
END

My ultimate goal, once I have confirmed the minimum mass of Solution 1 required to dissolve the minerals to at least equilibrium, what the associated dissolution rate would be.

Any guidance would be greatly appreciated.

Regards,

[dlparkhurst]

First, PHREEQC works best with about 1 kg of water. You may have numerical issues if the solution mass is very large. It is more awkward, but I would do the calculation with a liter of solution, and decreasing minerals to simulate greater solution:mineral ratios. 

Second, I don't understand this statement:

Code: [Select]

My ultimate goal, once I have confirmed the minimum mass of Solution 1 required to dissolve the minerals to at least equilibrium, what the associated dissolution rate would be.

There is no minimum mass of solution. Whatever mass of solution you use, each mineral will either react to equilibrium or completely dissolve.

Usually, the question you are asking is a transport question as to how many pore volumes are necessary to remove minerals, which is slightly different than your question because the dissolved products are swept away, whereas in your case the dissolved products remain in the solution.

If you have posed your question accurately, then this is the way I would do it. I've added a pseudo mineral "Constant" to be able to calculate solution:mineral ratios, and to make the plot that I think you described.

Code: [Select]

PRINT
-si false # turn back on if you need it
PHASES
Constant
NaCl = Na+ + Cl-
log_k 100
END
SOLUTION 1
    temp      65
    pH        5.5
    pe        4
    redox     pe
    units     mg/l
    density   1.051
    Al        0.04
    As        13
    B         44
    Ba        32
    Br        187
    Ca        7995
    Cl(-1)    64112
    Cs        18
    F         3
    Fe        25
    K         4205
    Li        10
    Mg        109
    Mn        28
    Na        28729
    Pb        1
    Rb        27
    S(6)      157
    Si        80
    Sr        428
    Zn        7
    -water    1 # kg
END

EQUILIBRIUM_PHASES 1-2
    Brucite   0 4801.122
    Calcite   0 4316.249
    Chalcedony 0 2446.738
    Fe(OH)2   0 44.51
    Mn(OH)2(am) 0 22.48
    Constant 0 1   pre
END
EQUILIBRIUM_PHASES_MIX 1
2 1e0
END
USE solution 1
USE equilibrium_phases 1
USER_GRAPH 1
    -headings               rxn Pyrochroite Fe(OH)2 Brucite Calcite Chalcedony
    -axis_titles            "Mass of DLS Brine, kg" "FINAL Assemblage" ""
    -axis_scale x_axis      auto auto auto auto log
    #-axis_scale y_axis      auto auto auto auto log
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 f = 1/EQUI("Constant")
20 GRAPH_X f
30 GRAPH_Y f * EQUI("Mn(OH)2(am)"), f * EQUI("Fe(OH)2"), f * EQUI("Brucite"), f *EQUI("Calcite"), f * EQUI("Chalcedony")
  -end
    -active                 true
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-1
END
USE solution 1
USE equilibrium_phases 1
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-2
END
USE solution 1
USE equilibrium_phases 1
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-3
END
USE solution 1
USE equilibrium_phases 1
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-4
END
USE solution 1
USE equilibrium_phases 1
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-5
END
USE solution 1
USE equilibrium_phases 1
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-6
END
USE solution 1
USE equilibrium_phases 1
END
EQUILIBRIUM_PHASES_MIX 1
2 1e-7
END
USE solution 1
USE equilibrium_phases 1
END


[DvS95]

Belated thank you for your assistance, David.