Anion exclusion in TRANSPORT calculations

[liamabrahamsen]

Has anyone attempted to model anion exclusion effects in PHREEQC? I'm trying to simulate a column experiment in which an anionic complex is eluted before a conservative tracer, i.e. at less than one pore volume. Not sure if it's possible. Is anyone aware of other codes that can do this?

Thanks,
Liam.

[dlparkhurst]

TRANSPORT has multicomponent diffusion capability, where there are ion-specific diffusion coefficients. It would be possible to speed up the diffusion of an ion by increasing its diffusion coefficient (although current is required to be zero, so a counter-ion must move along with the ion).

Sounds like you have an advective system. The only thing close is an enrichment factor for each ion that can be defined in SOLUTION_SPECIES, which controls the concentration of each ion in the diffuse double layer of surfaces.