Niedl.ppi
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# fit some Ni sorption to goethite data
SPECIATION
calculationType fit
calculationMethod 1
FIT
dataFile "Nisolnfresh.dat" # fit data file - fit the final Ni concn not the amount sorbed
dependentVariableColumnObs 2 # final Ni concn is in column 2 of fit data file
# NB this is often a good way of fitting sorption data where possible
dependentVariableColumnCalc 2 # calcd final Ni concn in column 2 of selected output
fitFiniteDiffStepSize 1.0E-02 # size of initial adjustment of parameters when fitting
fitConvergenceCriterion 1.0E-12
fitMaxStepSize 1.0
fitWeightingMethod 0 # 0 = unit weighting for all points
numberOfFitParameters 2
fitParameterNames "log_k1" "log_k2"
fitLogParameters 0 0 # 0 = linear parameters
fitAdjustableParameters 1 1 # 1 = adjustable
fitParameterValues 8. 0 # initial values of log_k1 and log_k2
PLOT
plotTitle "Ni sorption by goethite (edl)"
xoffset 60
xtitle pH
ytitle "soln Ni (mol/L)"
pxmin 4.0 # p or plot limits
pxmax 9.0
pymin 0
pymax 5.E-04
pydec 4 # number of decimal places
lineColor blue
lineWidth 0.4
lines calculated # calculated column from out file
points observed # observed column from out file
legendTextSize 1.9 # key size
pointSize 3.0
labelSize 0 # suppress labelling
customXcolumn 6 # column 6 of out file
extraText "extratextfitNi.dat"
CHEMISTRY
TITLE Goethite surface 1pK model, Ni sorption 1 site.
PHASES
Fix_H+
H+ = H+
log_k 0.
SURFACE_MASTER_SPECIES
Fes_ Fes_OH-0.5
SURFACE_SPECIES
Fes_OH-0.5 = Fes_OH-0.5 # surface charging
log_k 0.0
Fes_OH-0.5 + H+ = Fes_OH2+0.5
log_k 8.50
2Fes_OH-0.5 + Ni+2 = (Fes_OH)2Ni+ # bidentate model
log_k <log_k1>
2Fes_OH-0.5 + Ni+2 + H2O = (Fes_OH)2NiOH + H+
log_k <log_k2>
SELECTED_OUTPUT
high_precision true
reset false
USER_PUNCH
headings pH Ni
-start
10 punch -la("H+"), TOT("Ni") # pH and total dissolved Ni (calcd)
-end # fitting compares TOT("Ni") with obsd total, eg by ICP-AES
SURFACE 1
# -diffuse_layer
# -no_edl
Fes_OH-0.5 1.09e-3 32.7 3.33 # goethite parameters
SOLUTION 1
units mol/kgw
Ni 0.4258e-3 # NiT
Na 0.1 # background electrolyte
N(5) 0.1 charge
EQUILIBRIUM_PHASES
O2(g) -0.67 0.1
Fix_H+ -<pHobs> NaOH
-force_equality true
Ni(OH)2 0 0
END
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