flipper78

Thank you, Brian, for the very helpful information!

Hi together, now I a have a new problem. I try to model the dissolution of GdPO4:0.5H2O at pH 6 in contact with the atmosphere (fixed fugacities, fixed pH) at 25°C. The thermodynamic data is complete but I need advice regarding the correct data input. Something is wrong with the charge balance, since in the output it is said: "molality of Na+ component forced negative by charge balance". In the attached files you can find my input and output information. I would like to prevent that the Na+ is forced negative, so where is the error in the charge balance? Or is something else not correct? What I noticed is that it run is working better if the pH is not fixed (although it has in the result the same value as in "fixed mode"). However, still the Na molality is changed but not forced negative. Thank you in advance for the help.

Hi Brian, you are right, the pH is at 10.25 with the data I use(d).

Hello all, I am using React to model the dissolution of NdPO4 (input as reactant) under atmospheric conditions (fixed fugacities, fixed pH). The pH is adjusted with HNO3, therefore the NO3- concentration. With the input shown in the attached file "Dissolution pH 5" the program runs without any problems. In the next step, I would like to model the similar process at pH 10, again in atmospheric conditions. Here, of course, the pH would be adjusted via e.g. NaOH. I tried a few things, e.g. swapping H+ <-> OH- but somehow it will not work (see attachment Dissolution pH 10). Here, I set the OH- activity to 0.01 and this gives a pH of 10, although a a pH of 12 should be expected; especially if one looks at the OH- concentrations, e.g. after step 100 (= 0.016 mol/kg). Has anyone experience how I can input correctly the fixed pH of 10 while having normal atmospheric conditions? Thanks in advance for the help. Kind regards, Flipper78