BC_IITB

Hi, I am modelling a hypothetical ground water system (an ideal system used in published literature to study carnotite stability) and I have generated carnotite stability diagram as attached (Carnotite_Eh_pH.png). Now I am interested in modelling evolution of this system when it rises to the surface (i.e. evaporation, loss of CO2 etc). However the stability diagram was generated using species activities, while in the react program modelling is best performed using species concentrations. I tried modelling using the species activities but the program gave errors like large residual errors for certain species or that initial solution is too saturated with carnotite or uraninite (I tried changing some parameters alternatively to correct for the error, but in vain). Moreover charge balance was also not successfully acheived. I suppose that an alternative would be to calculate concentrations from activities by using the formula ai = yimi; where ai = activity, yi = activity coefficient and mi = molality. However on referring to Bethke (2007) I understood that, in GWB, for dilute solutions "yi" approaches to unity and hence "ai" becomes equivalent to "mi". I am a bit skeptical to use the activity values as molarity values directly in React program. Hence kindly suggest a rational way of going about this. I have attached the .rea file for reference (Carnotite_React_GWB.rea). Please have a look at it. My primary objective is to model carnotite precipitation from this system (see attached figure pH_vs_Mnrl_satrtn.png) but unfortunately carnotite mineral does not reach saturation or the error message that initial system in too saturated with carnotite appears. Hoping to receive helpful comments and suggestions. Many thanks, BC Carnotite_React_GWB.rea

Hello, I have an annual GWB student's licence for the "GWB-Essentials" package. I have been using GWB for studying stability and solubility of uranium ore mineral 'carnotite' as a function of pH and the product of ionic concentrations of the constituent elements. I have used ACT2 module to create the Eh-pH diagrams and demarcate the stability field of carnotite. However in continuation with my study I am now required to model the reactions and trace the reaction paths that cause precipitation of carnotite mineral in near surface conditions from oxidising ground waters. The main process that drive carnotite precipitation are fluid mixing and evaporation. Hence I need to simulate these processes in the surficial uranium mineral system model (environment). I have studied the online tutorials from the GWB website and I have understood that the "React" module of the GWB would be useful in modelling these processes. However in the student's package of GWB that I have, the "React" module is not activated. Hence please let me know how to access the "React module". I was wondering if a temporary trial version of the "React" module is available; this would enable me to check if it would help me in modelling the processes of my interest. Thanking in anticipation. -BC

Hello, I am studying stability and solubility of uranium ore mineral 'carnotite' as a function of pH and the product of ionic concentrations of the constituent elements. In case of carnotite the ionic species involved are uranium, vanadium and potassium. So I want to create a plot of ion product of uranium, vanadium and potassium on the Y axis against the pH values on the X-axis. I have used ACT2 module to create the Eh-pH diagrams and demarcate the stability field of carnotite. In this case the x-axis was pH and y-axis was Eh, and the other species were added in the box stating "in the presence of"; But now I want to add multiple species along the Y axis, so that the ion product plots on y-axis as the function of pH. Is there a way to add multiple ions along the y-axis and the pH on x-axis in ACT2? I have attached the figure that I am trying to recreate Any help would be highly appreciated.