I recently downloaded PHREEQC and am trying to come to terms with it (this is a chore in and of itself for me). At present I am attempting to utilize PHREEQC to investigate the reduction of Fe3+ and its various complexes by dihydroanathraquinone-2,6 disulfonate (AH2DS), which is the reduced form of anthraquinone-2,6-disulfonate (AQDS). We are following the oxidation of AH2DS to AQDS using a stopped-flow apparatus with UV/Vis detection. This is being done over a range of pH and Fe3+ concentrations.
The half-cell reduction of AQDS to AH2DS follows as: AQDS + 2e- + 2H+ = AH2DS E0 = 0.253 V
I was hoping to utilize PHREEQC first model the equilibrium solution composition of a solution initially containing Fe3+, NaClO4, and AH2DS - a very simple system. After multiple attempts of building an input file that identifies ClO4-, the FeClO42+ complex, AH2DS, and AQDS. I still can't get it to converge. The output appears not to recognize the AH2DS [in the attached output file this species is designated as A(2)]. Two questions: 1) is this a problem that PHREEQC can handle, and 2) if it should be able to do this problem, what am I missing?
I very much appreciate your help in this matter.
Cal Ainsworth, Ph.D.
Environmental dynamics and Simulations, MSIN K3-61
Pacific Northwest National Laboratory
P.O. Box 999
Richland, WA 99352
Phone: (509) 375-2670
Fax: (509) 375-6954
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 1623 since Jan 22, 1998.