FeAsS.ppi
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# predominance diagram for As in the presence of HFO which adsorbs As according to the Dzombak & Morel DL adsorption model
SPECIATION
calculationType ht1
calculationMethod 1
mainSpecies As
xmin 2.0 # range of pH
xmax 12.0
ymin -90.0 # range of log fO2(g) to control redox
ymax 0.0
resolution 500 # controls the resolution (big resolution means small step size)
PLOT
plotTitle "Fe-As-S-H<sub>2</sub>O (HFO DLM)"
xtitle pH
ytitle "log <i>f </i>O<sub>2</sub>(g)"
extratext extratextFeAsS.dat
CHEMISTRY
# simulation 1
include 'ht1.inc' # standard predominance-calculating file
SOLUTION 1 # initial solution calculation
Temp 20
pH 1.8
units mol/kgw
Fe(2) 3.5e-1 # total concns
As 1e-2
S(6) 1e-2 # sulphide minerals can form but not adsorb
Na 1e-1
Cl 1e-1
END
include 'hfo.inc'
KNOBS # NB this only applies to this (2nd) simulation
-convergence_tolerance 1e-10 # the default 1e-12 causes a lack of convergence at pH 9.55 and logO2(g) -84.7
# simulation 2
USE solution 1
EQUILIBRIUM_PHASES 1
Fix_H+ -<x_axis> NaOH
-force_equality true
O2(g) <y_axis> 0.1
As_native 0 0 # most likely minerals given the database
Orpiment 0 0 # hematite, magnetite removed to make goethite stable
Realgar 0 0
As2S3(am) 0 0
Pyrite 0 0
Arsenolite 0 0
Claudetite 0 0
Mackinawite 0 0
FeS(ppt) 0 0
Sulfur 0 0
Fe(OH)3(a) 0 0
Greigite 0 0
Scorodite 0 0
Mirabilite 0 0
Melanterite 0 0
Thenardite 0 0
As2O5(cr) 0 0
Jarosite-Na 0 0
JarositeH 0 0
# Goethite 0 0
END
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