Allophane missing from database

[hsosno1]

Hi people !

We are modelling the adsorption of fluoride on allophane in Kenyan andosoils, unfortunately allophane is not available in phreeqc's database.
We thought about using the keyword master species to integrate it into the program, but don't know how do use this keyword properly...
Could you help us ?

[dlparkhurst]

If you treat allophane as a SURFACE, then you need to define SURFACE_MASTER_SPECIES to identify a surface and SURFACE_SPECIES data block to define reactions and thermodynamic constants. Hfo in phreeqc.dat would serve as an example. The number of sites, surface area, and initial composition of a surface are defined with the SURFACE data block.

If you want to relate the surface to a reacting phase to allow allophane to dissolve and precipitate resulting in the number of surface sites and surface area to vary, then you need to define the thermodynamic data for allophane in PHASES, and include an EQUILIBRIUM_PHASES data block, in addition to the SURFACE data block.