surfacearea.ppi
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# calculates how the solution concn of As changes as the surface area of Hfo
# (but not the surface properties) is reduced in a closed system.
SPECIATION
JobTitle "Diagenesis"
calculationType custom
calculationMethod 1
xmin 10.0 # minimum surface area, see below
xmax 600.0 # maximum surface area
resolution 100
numericTags <mass> = 1 \
<molecular_wt> = 89 \
<initial_site_density_per_mol> = 0.2 \
<initial_surface_area> = 600 \
<initial_site_density_per_g> = <initial_site_density_per_mol>/<molecular_wt> \
<initial_sites> = <initial_site_density_per_g>*<mass> \
<site_density_per_m2> = <initial_site_density_per_g>/<initial_surface_area> \
<surface_area> = <x_axis> \
<sites> = <surface_area>*<site_density_per_m2>*<mass>
PLOT
plotTitle "As desorption as the surface area decreases"
xtitle "Surface area (m<sup>2</sup> g<sup>-1</sup>)"
ytitle "As (\mg L<sup>-1</sup>)"
pymax 5000.0 # truncate the highest values
customxColumn surface_area
lines As
lineWidth 0.6
lineColor red
legendTextSize 0.0
extraText "extratextsurfacearea.dat"
CHEMISTRY
PRINT
# -reset false
PHASES
Fix_H+
H+ = H+
log_k 0.0
SELECTED_OUTPUT
-high_precision true
-reset false
USER_PUNCH
-headings totAs totP
-start
10 totAs=SYS("As",n,n$,t$,c)
20 totP=SYS("P",n,n$,t$,c)
30 punch totAs, totP
-end
# first simulation - set up initial conditions
SOLUTION 1
temp 25
pH 7.0
units mol/kgw
density 1
Na 1e-2
N(5) 1e-2
# Equilibrate Hfo with low As and P
As 1 ug/kgw
P 0 ug/kgw # P has an important effect
-water 1 kg
EQUILIBRIUM_PHASES 1
Fix_H+ -7.0 NaOH 10
-force_equality true
O2(g) -0.67 10
SURFACE 1
Hfo_w <initial_sites> <initial_surface_area> <mass>
-equilibrate 1
END
# second simulation - now start reducing surface area always starting from the initial state
USER_PUNCH
-headings surface_area As
-start
10 As=tot("As")*74.9216*1e6
20 punch <surface_area> As
-end
SOLUTION 1
temp 25
pH 7.0
units mol/kgw
density 1
Na 1e-2
N(5) 1e-2
As <totAs> # tag name from selected output file headings above
P <totP> # mol/kgw
-water 1 # kg
EQUILIBRIUM_PHASES 1
Fix_H+ -7.0 NaOH 10 # keep a constant pH
O2(g) -0.67 10
SURFACE 1
Hfo_w <sites> <surface_area> <mass>
END
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