Keywords

SURFACE_SPECIES

Example

Line 0:  SURFACE_SPECIES 
Line 1a: Surf_sOH = Surf_sOH
Line 2a       log_k     0.0
Line 1b: Surf_sOH + H+ = Surf_sOH2+
Line 2b:      log_k     6.3
Line 1c: Surf_wOH = Surf_wOH
Line 2c       log_k     0.0
Line 1d: Surf_wOH + H+ = Surf_wOH2+
Line 2d:      log_k     4.3
Line 1e: Surf_sOH + UO2+2 = (Surf_s2O2)UO2 + 2H+
Line 2e:      log_k     -2.57
Line 3:       -no_check 
Line 4:       -mole_balance (Surf_sO)2UO2

Explanation

Keyword for the data block. No other data are input on the keyword line.

Association reaction for surface species. The defined species must be the first species to the right of the equal sign. The association reaction must precede all identifiers related to the surface species. Line 1a is the master-species identity reaction.

log_k--identifier for log K at 25^oC. Optionally, -log_k, logk, -l[og_k], or -l[ogk].

log K--Log K at 25^oC for the reaction. Default 0.0. Log K for a master species is 0.0.

-no_check--indicates the equation defining the aqueous species should not be checked for charge and elemental balance. Optionally, no_check, or -n[o_check]. By default, all equations are checked. The only exceptions might be for bidentate surface sites. However, the identifier -mole_balance is needed to ensure that the proper number of atoms of each element and moles of surface sites are included in mole-balance equations.

-mole_balance--Indicates the stoichiometry of the species will be defined explicitly. Optionally, mole_balance, mass_balance, mb, -m[ole_balance], -mass_balance, -m[b].

formula--chemical formula defining the stoichiometry of the species. Normally, both the stoichiometry and mass-action expression for the species are determined from the chemical equation that defines the species. Rarely, it may be necessary to define the stoichiometry of the species separately from the mass-action equation. Sorption of uranium on iron oxides as described by Waite and others (1994) provides an example. They use different coefficients in the mass-action equation than the mole-balance equations. The chemical equation defining the species (Line 1e) is used to obtain the mass-action expression. By default, the formula for the species is derived from the sum of all the species in the equation excluding the defined surface species. The -mole_balance identifier is used to specify explicitly the stoichiometry of the surface species (Line 4).

Notes

An underscore plus one or more lowercase letters is used to define different binding sites for the same surface. In the example, association reactions for a strong and a weak binding site are defined for the surface named "Surf." Multiple surfaces may be defined simply by defining multiple master surface species (for example, Surfa, Surfb, and Surfc). Multiple binding sites can be defined for each surface. Association reactions for each surface and binding site must be defined with SURFACE_SPECIES input.

Temperature dependence of log K can be defined with enthalpy of reaction (identifier delta_h) and the van't Hoff equation or with an analytical expression (-analytical_expression). See SOLUTION_SPECIES or PHASES for examples.

The identifier -no_check can be used to disable checking charge and elemental balances (see SOLUTION_SPECIES). The use of -no_check is not recommended. If -no_check is used, then the -mole_balance identifier is needed to ensure the correct stoichiometry for the surface species.

Example problems

Related keywords

Example

Explanation

Notes

Example problems

Related keywords

Generated with CERN WebMaker