Thanks for your recent help on executing phreeqci.
I have another problem that I hope you can help me with: I have mixed a groundwater with 129 ppm SO4-2 (specified as S) with Fe_metal and observed that the water reaches saturation with respect to several Fe oxide and sulfide phases and as well as As2S3. As expected, pe drops like a rock. Magenite has the greatest degree of saturation of the Fe phases.
Allowing magnetite, pyrite, and orpiment to "exist" shows that only magnetite ppts, leaving pH high but perhaps unrealistically high (12+) so that HS- is trivial relative to other S species and the sulfides do not form.
Do I need to define reactions for the other S species and the orpiment, pyrite, etc.?
Also, can you comment on reaction precipitation sequence?
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