1D Surface complexation¶
Overview and Capabilities tested¶
This test example performs the simulation of \(\ce{Zn^{2+}}\) surface complexation on weak and strong iron hydroxide sites in a 1D flow domain.
1D flow
1D advective transport
Geochemical reactions
Aqueous complexation reactions (equilibrium)
Surface complexation reactions (equilibrium)
For details on this test, see About.
Background¶
Introduction¶
Description of surface complexation… The simulation is run to 50 years.
Model¶
Flow and transport¶
See the 1D Conservative tracer transport example.
Aqueous complexation¶
Five equilibrium reactions are considered in aqueous phase that include the aqueous speciation of \(\ce{Zn^{2+}}\) (by convention, secondary species are given in the left hand side, while primary species are in the right hand side):
\(\ce{OH^- <=> H_2O - H^+}\), \(\; log(K)=13.9951\)
\(\ce{Zn(OH)_{2(aq)} <=> 2 H_2O - 2 H^+ + Zn^{2+}}\), \(\; log(K)=17.3282\)
\(\ce{Zn(OH)_3^- <=> 3 H_2O - 3 H^+ + Zn^{2+}}\), \(\; log(K)=28.8369\)
\(\ce{Zn(OH)_4^{2-} <=> 4 H_2O - 4 H^+ + Zn^{2+}}\), \(\; log(K)=41.6052\)
\(\ce{ZnOH^+ = H_2O -1 H^+ + 1 Zn^{2+}}\), \(\; log(K)=8.96\)
Surface complexation¶
Two distinct iron hydroxide (\(\ce{FeOH}\)) surface sites are available for sorption of \(\ce{Zn^{2+}}\): weak \(\ce{({>}FeOH_{w})}\) and strong \(\ce{({>}FeOH_{s})}\). Surface site concentrations for \(\ce{>FeOH_{w}}\) and \(\ce{>FeOH_{s}}\) are defined in ‘Material Properties’. No explicit definition of the mineral phase on which \(\ce{Zn^{2+}}\) is required.
In total, six surface complexation reactions are considered:
\(\ce{{>}FeOH_{2w}^+ <=> {>}FeOH_{w} + H^+}\), \(\; log(K)=-7.18\)
\(\ce{{>}FeO^{-}_{w} <=> {>}FeOH_{w} - H^+}\), \(\; log(K)=8.82\)
\(\ce{{>}FeOHZn^{+}_{w} <=> {>}FeOH_{w} - H^+ + Zn^{2+}}\), \(\; log(K)=2.32\)
\(\ce{{>}FeOH_{2s}^+ <=> {>}FeOH_{s} + H^+}\), \(\; log(K)=-7.18\)
\(\ce{{>}FeO^{-}_{s} <=> {>}FeOH_{s} - H^+}\), \(\; log(K)=8.82\)
\(\ce{{>}FeOHZn^{+}_{s} <=> {>}FeOH_{s} - H^+}\) \(\; log(K)=-0.66\)
Problem Specification¶
Flow and transport¶
See the 1D Conservative tracer transport example.
Geochemistry¶
To do.
About¶
Benchmark simulator: PFlotran
Files:
Amanzi input file: amanzi-u-1d-surface-complexation.xml
Benchmark simulator input file: 1d-surface-complexation.in
Location: amanzi/examples/examples/phase2/chemistry/1d-surface-complexation
Author: B. Andre, G. Hammond
Testing and Documentation: S. Molins
Last tested on Aug 31 2013