I have a question about the geochemistry of groundwater around contaminated sites, such as landfills. I am using the Geochemists Workbench software to model certain sites, using the model to produce Pourbaix Diagrams to assess whether the groundwater is supersaturated with certain minerals. Most of our sites have issues with dissolved cobalt and nickel. The diagrams for one of my sites indicates that the groundwater is supersaturated with respect to cobalt ferrite, limiting the dissolved cobalt concentrations in the groundwater. However, I cannot find much, if any, literature on this precipitate relative to its presence in natural environments like groundwater. I don’t believe the cobalt ferrite precipitate is actually forming at the site. The same goes for nickel ferrite (trevorite) which is a rare mineral. I can suppress these compounds within the model and, when this is done, the dominant precipitate forming is hematite, which I do believe is most likely occurring.
Do you have any information or insight into these two ferrite compounds and whether or not these can actually form in groundwater and remain stable?