[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: PHREEQC problem

Sorry I didn't explain the process clearly. I assume the sorption of Cu by
organicmatter site (Org_x) as follow (see Table 6.6, Werner Stumm, 1995, the
book: Aquatic Chemistry):
Cu+2  + Org_xH2  =  Org_xCu  + 2H+
To the formula of Org_xh,  I mean H is 0 (zero), not H O. Maybe as you said,
it's not necessary to mention this kinetic expression as it has the same rate
like Org_xcu.

cheers, xiaomin

David L Parkhurst wrote:

> >About (1), I don't understand why you write: H -2 Cu +1 OH -1. I write in
> the kinetic expression:
>  -Formula  H -2.0 Cu +1
> will it be any problem?
> I combined your two expressions ( Org_xcu and Org_xh) because they have the
> same rate expression. The combined formulas do not appear to be charge
> balanced to me.
> Your calculated rate is negative I believe, so with -formula H -2 Cu +1,
> you would be removing copper and adding H to solution. For Org_xh the rate
> is positive, so with -formula O H, you are adding OH to solution. The net
> reaction is relative to solution is Cu -1 H +2 OH +1 or Cu -1 H +3 O +1.
> What is the reaction that you are trying to model?
> SOH + Cu+2 = SOCu+ + H+ ?
> You probably need to add the counter ion for such a reaction to make sure
> the solution does not get imbalanced. (SURFACE calculations add an inert
> charge to account for this effect.)
> SOH + Cu+2 + Cl- = SOCuCl + H+
> So the -Formula  CuCl -1 H +1 would be appropriate. But maybe this is not
> what your are trying to model.
> > To (2), I think I have noticed the difference. TOT is used to get the
> concentration of Cu in the solution which is required according to the
> model. As the water in each cell is only 0.03375 kg, the organic matter is
> calculated based on the quantity of soil and ratio of organic matter in
> each cell. therefore, it seems not to be the problem.
> If you say so. I would still try a simpler rate expression to see whether
> the problem is in the rate expression or some other part of the kinetic
> definition.
> David
> David Parkhurst (dlpark@xxxxxxxx)
> U.S. Geological Survey
> Box 25046, MS 413
> Denver Federal Center
> Denver, CO 80225
> Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled

Project Home Page
Complete Water Resources Division Software
USGS Home Page
Water Resources Division Home Page
NRP Home Page
Help Page
USGS Privacy Statement       

Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. 

The URL of this page is: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/mail/msg00645.html
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 2548 since Jan 22, 1998.