rate for surface complexation

[hamiderfani]

Hello everybody
hope you are doing very well and thanks for your reply in advance.
I have a question regarding the surface complexation in Phreeqc.
I have a SCM and it works very well. I wanted to know if there is any way to assign a rate equation (something like a langmuir type rate equation) to reactions in SCM?
In reality the response is never instantaneous on the surface so in this way I hope to be able to impose some delay to the effect on surface properties.
Any other way to impose a delay on the surface properties is also welcome.

Thanks

[dlparkhurst]

Yes, you can use KINETICS to simulate kinetic sorption, although it is not very easy.

Attached is a file that kinetically sorbs a constituent "A" using a Langmuir isotherm. The idea is to calculate what surface sorption would be given the dissolved concentration and use the difference between that and what is actually sorbed to formulate a rate equation.

Also attached is an example of kinetic sorption for a surface complexation example. It is not my example, and it has been a long time since I looked at it, so you are on your own to decipher it. Hopefully, it works.