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Re: Adsorption kinetics in phreeqc

Here is a file I made to perform case C (first-order reversible) in a
simple advective transport case. The concentrations S in your table are
moles per kg solid, but are in units of moles/kgw in PHREEQC, which removes
the factors theta/ro from the equations. The example has a Kd of 10 (= S/C)
and a forward rate constant of 1/day. The backward rate constant is found
from Kd = kf/kr.

You may have a problem if you have a big discrepancy between kf and the
time step, for example seconds for kf and years for transport time steps.
In this case, you should probably use equilibrium sorption. My example has
kf = 1/day and time steps of days.


(See attached file: kinsorb.pqi)

David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

                      Alan H Welch                                                                             
                                               To:      David L Parkhurst/WRD/USGS/DOI@xxxx                    
                      09/11/01 10:43           cc:      Lawrence S Feinson/WRD/USGS/DOI@xxxx, Kenneth G        
                      AM                       Stollenwerk/WRD/USGS/DOI@xxxx                                   
In-Reply-To: <OF834F57B7.B3127FCD-ON88256AC4.005AC381@xxxxxxxx>
                                               Subject: Adsorption kinetics in phreeqc                         


I am interested in modeling arsenic adsorption kinetics (on iron oxide)
using phreeqc. Do you have an example of how to code adsorption kinetics?
The rate model and symbols for the equations are in the attachments. Thanks
for the help.

(See attached file: rate.bmp)(See attached file: rate.symbol.bmp)

Best regards,

Alan Welch
U.S.Geological Survey
333 W. Nye Lane
Carson City, NV  89706

Office:  (775) 887-7609
FAX:  (775) 887-7629

Attachment: kinsorb.pqi
Description: Binary data

Attachment: rate.bmp
Description: Binary data

Attachment: rate.symbol.bmp
Description: Binary data

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