hfoCax.ppi
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# produces a set of predominance diagrams for Ca using the <loop> variable to systematically vary the total Fe in the system
# system contains a reduced Fe mineral
# Ca is present in solution, on an ion exchanger (eg clay), sorbed by Fe(OH)3(a) and potentially in a mineral (calcite)
SPECIATION
jobTitle "Fe-Ca-H2O redox"
calculationType ht1 # produce a predominance diagram using the hunt and track approach
calculationMethod 1
mainSpecies Ca Fe # diagram for Ca
xmin 2.0 # pH range adjusted through the <x_axis> variable
xmax 10.0
ymin -80.0 # f(O2(g)) range adjusted through the <y_axis> variable
ymax 0.0
resolution 50 # low resolution - jumps around on a 50 x 50 grid
loopMin 0.0 # min, max and step size for FeT (the z-loop variable)
loopMax 0.1
loopInt 5.0E-02
PLOT
plotTitle "Ca-Fe-Na with sorption and ion exchange<br>(includes Fe(OH)2(s) from llnl.dat)"
xtitle pH
ytitle "log <i>f</i> O<sub>2</sub>(g)"
pxmax 10.0
extraText "extratextFeOHCa.dat" # additional text on the plot
multipageFile F # each plot in a separate file
CHEMISTRY
include 'ht1.inc' # standard predominance calculating file
PHASES # temporarily add this to the database
Fe(OH)2(a) # from llnl.dat (NB approximate only - not checked for consistency)
Fe(OH)2 + 2.0000 H+ = + 1.0000 Fe++ + 2.0000 H2O
log_k 13.9045
-delta_H -95.4089 kJ/mol # Calculated enthalpy of reaction
-analytic -8.6666e+001 -1.8440e-002 7.5723e+003 3.2597e+001 1.1818e+002
SOLUTION 1
temp 25
pH 1.5
units mol/kgw
Fe(3) <loop> # FeT is controlled by the <loop> variable
Na 1e-2
Cl 1e-2 charge
Ca 1e-3 # CaT
EXCHANGE
-equilibrate 1
X 0.02 # 0.02 equiv of an exchanger
EQUILIBRIUM_PHASES 1
Fix_H+ -<x_axis> NaOH # x-axis is pH
-force_equality true
O2(g) <y_axis> # y-axis is log fO2(g)
CO2(g) -2 0.3 # soil PCO2 - max CO2 supplied is 0.3 mol
Fe(OH)3(a) 0 0 # possible minerals
Fe(OH)2(a) 0 0 # ... added to database above
Calcite 0 0
SURFACE 1
Hfo_sOH Fe(OH)3(a) equilibrium_phase 0.005 53300
Hfo_wOH Fe(OH)3(a) equilibrium_phase 0.2
END
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