Hello Dr. Parkhurst:
I am currently doing some solubility studies of clay minerals and I want to use the phrqeeqc code to simulate what is occurring in the reactions. problem is I have tried several different ways to describe the system to phrqeeqc and have collected the resulting outputs but I am not sure if the method I am using is best suited for what I am looking for since none of the test cases threats this problem directly. in addition, comparison with other speciation codes is a little difficult because of my uncertainty.
I am therefore hoping that you can give me some insight.
a typical run involves adding:
~2.0g Solid A + ~2.0g Solid B to 30ml of equil. solution (1.0 M MgCl2 + 0.001 M HCl; initial pH = 3.412) and seal in a LDPE bottle and allowed to equilibrate for several days.
1) What is the best approach you would suggest in defining this system to Phrqeeqc?
2) Which pH sould I be using? the initial pH or the final pH (pH at the end of run)
What is the best approach for multiple runs, each having a different quantity of starting solid, or a different volume of solution with a different initial pH (and subsequently different final pH). I have tried SOLUTION_SPREAD keyword but to handled all the variations in the runs I would have to use multiples.
e.g. in the above run: Solid A = 2.0g, 2.3g, 1.6g, 1.8g and 2.5g
Solid B = 2.0g, 1.2g, 1.7g, 2.3g, and 2.2g
Vol. = 10ml, 15ml, 20ml, and 30 ml.
initial pH = 3.412, 7.800, 10.235
from my understanding, I would have to describe three solutions, two phases for each quantity, or am I wrong. I am having a problem with the treatment of a fixed amt. of a solids in a fixed vol. of solution at a specific starting pH vs. describing the ending solution.
any suggestions would be helpful, thanks in advance.
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:
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 1168 since Jan 22, 1998.